Divorced Dads And Their Daughters

Despite common assumptions, parents have less of an impact on their children’s future development than they’re often credited with. Twins reared apart usually aren’t much different than twins reared together, and adopted children don’t end up resembling their adoptive parents substantially more than strangers. While parents can indeed affect their children’s happiness profoundly, a healthy (and convincing) literature exists supporting the hypothesis that differences in parenting behaviors don’t do a whole lot of shaping in terms of children’s later personalities (at least when the child isn’t around the parent; Harris, 2009). This makes a good deal of theoretical sense, as children aren’t developing to be better children; they’re developing to become adults in their own right. What children learn works when it comes to interacting with their parents might not readily translate to the outside world. If you assume your boss will treat you the same way your parents would, you’re likely in for some unpleasant clashes with reality. 

“Who’s a good branch manager? That’s right! You are!”

Not that this has stopped researchers from seeking to find ways that parent-child interactions might shape children’s future personalities, mind you. Indeed, I came upon a very new paper purporting to do just that this last week. It suggested that the quality of a father’s investment in his daughters causes shifts in his daughter’s willingness to engage in risky sexual behavior (DelPriore, Schlomer, & Ellis, 2017). The analysis in the paper is admittedly a bit tough to follow, as the authors examine three- and even four-way interactions (which are difficult to keep straight in one’s mind: the importance of variable A changes contingent on the interaction between B, C, & D), so I don’t want to delve too deeply into the specific details. Instead, I want to discuss the broader themes and design of the paper.

Previous research looking at parenting effects on children’s development often suffers from the problem of relatedness, as genetic similarities between parents and children make it hard to tease apart the unique effects of parenting behaviors (how the parents treat their children) from natural resemblances (nice parents have nice children). In a simple example, parents who love and nurture their children tend to have children who grow up kinder and nicer, while parents who neglect their children tend to have children who grow up to be mean. However, it seems likely that parents who care for their children are different in some important regards than those who neglect them, and those tendencies are perfectly capable of being passed on through shared genes. So are the nice kids nice because of how their parents treated them or because of inheritance? The adoption studies I mentioned previously tend to support the latter interpretation. When you control for genetic factors, parenting effects tend to drop out.

What’s good about the present research is its innovative design to try and circumvent this issue of genetic similarities between children and parents. To accomplish this goal, the authors examined (among other things) how divorce might affect the development of different daughters within the same family. The reasoning for doing so seems to go roughly as follows: daughters should base their sexual developmental trajectory, in part, on the extent of paternal investment they’re exposed to during their early years. When daughters are regularly exposed to fathers that invest in them and monitor their behavior, they should come to expect that subsequent male parental investment will be forthcoming in future relationships and avoid peers who engage in risky sexual behavior. The net result is that such daughters will engage in less risky sexual behavior themselves. By contrast, when daughters lack proper exposure to an investing father, or have one who does not monitor their peer behavior as tightly (due to divorce), they should come to view future male investment as unlikely, associate with those who engage in riskier sexual behavior, and engage in such behavior themselves.

Accordingly, if a family with two daughters experiences a divorce, the younger daughter’s development might be affected differently than the older daughter’s, as they have different levels of exposure to their father’s investment. The larger this age gap between the daughters, the larger this effect should be. After recruiting 42 sister pairs from intact families and 59 sister pairs from divorced families and asking them some retrospective questions about what their life was like growing up, this is basically the result the authors found. Younger daughters tended to receive less monitoring than older daughters in families of divorce and, accordingly, tended to associate with more sexually-risky peers and engage in such behaviors themselves. This effect was not present in biologically intact families. Do we finally have some convincing evidence of parenting behaviors shaping children’s personalities outside the home?

Look at this data and tell me the first thing that comes to your mind

I don’t think so. The first concern I would raise regarding this research is the monitoring measure utilized. Monitoring, in this instance, represented a composite score of how much information the daughters reported their parents had about their lives (rated from (1) didn’t know anything, (2) knew a little, or (3) knew a lot) in five domains: who their friends were, how they spent their money, where they spent their time after school, where they were at night, and how they spent their free time. While one might conceptualize that as monitoring (i.e., parents taking an active interest in their children’s lives and seeking to learn about/control what they do), it seems that one could just as easily think of that measure as how often children independently shared information with their parents. After all, the measure doesn’t specify, “how often did your parents try to learn about your life and keep track of your behavior?” It just asked about how much they knew.

To put that point concretely, my close friends might know quite a bit about what I do, where I go, and so on, but it’s not because they’re actively monitoring me; it’s because I tell them about my day voluntarily. So, rather than talking about how a father’s monitoring of his daughter might have a causal effect on her sexual behavior, we could just as easily talk about how daughters who engage in risky behavior prefer not to tell their parents about what they’re doing, especially if their personal relationship is already strained by divorce.

The second concern I have concerns divorce itself. Divorce can indeed affect the personal relationships of children with their parents. However, that’s not the only thing that happens after a divorce. There are other effects that extend beyond emotional closeness. An important example of these other factors are the financial ones. If a father has been working while the mother took care of the children – or if both parents were working – divorce can result in massive financial hits for the children (as most end up living with their mother or in a joint custody arrangement). The results of entering additional economic problems into an already emotionally-upsetting divorce can entail not only additional resentment between children and parents (and, accordingly, less sharing of information between them; the reduced monitoring), but also major alterations to the living conditions of the children. These lifestyle shifts could include moving to a new home, upsetting existing peer relations, entering new social groups, and presenting children with new logistical problems to solve.

Any observed changes in a daughter’s sexual behavior in the years following a divorce, then, can be thought of as a composite of all the changes that take place post-divorce. While the quality and amount of the father-daughter relationship might indeed change during that time, there are additional and important factors that aren’t controlled for in the present paper.

Too bad the house didn’t split down the middle as nicely

The final concern I wanted to discuss was more of a theoretical one, and it’s slightly larger than the methodological points above. According to the theory proposed at the beginning of the paper:

“…the quality of fathering that daughters receive provides information about the availability and reliability of male investment in the local ecology, which girls use to calibrate their mating behavior and expectations for long-term investment from future mates.”

This strikes me as a questionable foundation for a few reasons. First, it would require that the relationship of a daughter’s parents are substantially predictive of the relationships she is likely to encounter in the world with regard to male investment. In other words, if your father didn’t invest in your mother (or you) that heavily (or at least during your childhood), that needs to mean that many other potential fathers are likely to do the same to you (if you’re a girl). This would further require, then, that male investment be appreciably uniform across time in the world. If male investment wasn’t stable between males and across time within a given male, then trying to predict the general availability of future male investment from your father’s seems like a losing formula for accuracy.

It seems unlikely the world is that stable. For similar reasons, I suggested that children probably can’t accurately gauge future food availability from their access to food at a young age. Making matters even worse in this regard is that, unlike food shortages, the presence or absence of male parental investment doesn’t seem like the kind of thing that will be relatively universal. Some men in a local environment might be perfectly willing to invest heavily in women while others are not. But that’s only considering the broad level: men who are willing to invest in general might be unwilling to invest in a particular woman, or might be willing or unwilling to invest in that woman at different stages in her life, contingent on her mate value shifting with age. Any kind of general predictive power that could be derived about men in a local ecology seems weak indeed, especially if you are basing that decision off a single relationship: the one between your parents. In short, if you want to know what men in your environment are generally like, one relationship should be as informative as another. There doesn’t seem to be a good reason to assume your parents will be particularly informative.

Matters get even worse for the predictive power of father-daughter relationships when one realizes the contradiction between that theory and the predictions of the authors. The point can be made crystal clear simply by considering the families examined in this very study. The sample of interest was comprised of daughters from the same family who had different levels exposure to paternal investment. That ought to mean, if I’m following the predictions properly, that the daughters – the older and younger one – should develop different expectations about future paternal investment in their local ecology. Strangely, however, these expectations would have been derived from the same father’s behavior. This would be a problem because both daughters cannot be right about the general willingness of males to invest if they hold different expectations. If the older daughter with more years of exposure to her father comes to believe male investment will be available and the younger daughter with fewer years of exposure comes to believe it will be unavailable, these are opposing expectations of the world.

However, if those different expectations are derived from the same father, that alone should cast doubt on the ability of a single parental relationship to predict broad trends about the world. It doesn’t even seem to be right within families, let alone between them (and it’s probably worth mentioning at this point that, if children are going to be right about the quality of male investment in their local ecology more generally, all the children in the same area should develop similar expectations, regardless of their parent’s behavior. It would be strange for literal neighbors to develop different expectations of general male behavior in their local environment just because the parents of one home got divorced while the other stayed together. Then again, it should strange for daughters of the same home to develop different expectations, too).

Unless different ecologies have rather sharp boarders

On both a methodological and theoretical level, then, there are some major concerns with this paper that render its interpretation suspect. Indeed, at the heart of the paper is a large contradiction: if you’re going to predict that two girls from the same family develop substantially different expectations about the wider world from the same father, then it seems impossible that the data from that father is very predictive of the world. In any case, the world doesn’t seem as stable as it would need to be for that single data point to be terribly useful. There ought not be anything special about the relationship of your parents (relative to other parents) if you’re looking to learn something about the world in general.

While I fully expect that children’s lives following their parents divorce will be different – and those differences can affect development, depending on when they occur – I’m not so sure that the personal relationship between fathers and daughters is the causal variable of primary interest.

References: DelPriore, D., Schlomer, G., & Ellis, B. (2017). Impact of Fathers on Parental Monitoring of Daughters and Their Affiliation With Sexually Promiscuous Peers: A Genetically and Environmentally Controlled Sibling Study. Developmental Psychology. Advance online publication. http://dx.doi.org/10.1037/dev0000327

Harris, J. (2009) The Nurture Assumption: Why Children Turn Out the Way They Do. Free Press, NY.

Why Do So Many Humans Need Glasses?

When I was very young, I was given an assignment in school to write a report on the Peregrine Falcon. One interesting fact about this bird happens to be that it’s quite fast: when the bird spots prey (sometimes from over a mile away) it can enter into a high-altitude dive, reaching speeds in excess of 200 mph, and snatch its prey out of midair (if you’re interested in watching a video of such a hunt, you can check one out here). The Peregrine would be much less capable of achieving these tasks – both the location and capture of prey – if its vision was not particularly acute: failures of eyesight can result in not spotting the prey in the first place, or failing to capture it if distances and movements aren’t properly tracked. For this reason I suspect (though am not positive) that you’ll find very few Peregrines that have bad vision: their survival depends very heavily on seeing well. These birds would probably not be in need of corrective lens, like the glasses and contacts that humans regularly rely upon in modern environments. This raises a rather interesting question: why do so many humans wear glasses?

And why does this human wear so many glasses?

What I’m referring to in this case is not the general degradation of vision with age. As organisms age, all their biological systems should be expected to breakdown and fail with increasing regularity, and eyes are no exception. Crucially, all these systems should be expected to all breakdown, more-or-less, at the same time. This is because there’s little point in a body investing loads of metabolic resources into maintaining a completely healthy heart that will last for 100 years if the liver is going to shut down at 60. The whole body will die if the liver does, healthy heart (or eyes) included, so it would be adaptive to allocate those development resources differently. The mystery posed by frequently-poor human eyesight is appreciably different, as poor vision can develop early in life; often before puberty. When you observe apparent maladaptive development early in life like that, it requires another type of explanation.

So what might explain why human visual acuity appears so lackluster early in life (to the tune of over 20% of teenagers using corrective lenses)? There are a number of possible explanations we might entertain. The first of these is that visual acuity hasn’t been terribly important to human populations for some time, meaning that having poor eyesight did not have an appreciable impact on people’s ability to survive and reproduce. This strikes me as a rather implausible hypothesis on the face of it not only because vision seems rather important for navigating the world, but also because it ought to predict that having poor vision should be something of a species universal. While 20% of young people using corrective lenses is a lot, eyes (and the associated brain regions dedicated to vision) are costly organs to grow and maintain. If they truly weren’t that important to have around, then we might expect that everyone needs glasses to see better; not just pockets of the population. Humans don’t seem to resemble the troglobites that have lost their vision after living in caves away from sunlight for many generations.

Another possibility is that visual acuity has been important – it’s adaptive to have good vision – but people’s eyes fail to develop properly sometimes because of development insults, like infectious organisms. While this isn’t implausible in principle – infectious agents have been known to disrupt development and result in blindness, deafness, and even death on the extreme end – the sheer numbers of people who need corrective lenses seem a bit high to be caused by some kind of infection. Further, the numbers of younger children and adults who need glasses appear to have been rising over time, which might seem strange as medical knowledge and technologies have been steadily improving. If the need for glasses is caused by some kind of infectious agent, we would need to have been unaware of its existence and not accidentally treated it with antibiotics or other such medications. Further, we might expect glasses to be associated with other signs of developmental stress, like bodily asymmetries, low IQ, or other such outcomes. If your immune system didn’t fight off the bugs that harmed your eyes, it might not be good enough to fight off other development-disrupting infections. However, there seems to be a positive correlation between myopia and intelligence, which would be strange under a disease hypothesis.

The negative correlation with fashion sense begs for explanation, too

A third possible explanation is that visual acuity is indeed important for humans, but our technologies have been relaxing the selection pressures that were keeping it sharp. In other words, since humans invented glasses and granted those who cannot see as well a crutch to overcome this issue, any reproductive disadvantage associated with poor vision was effectively removed. It’s an interesting hypothesis that should predict people’s eyesight in a population begins to get worse following the invention and/or proliferation of corrective lenses. So, if glasses were invented in Italy around 1300, that should have lead to the Italian population’s eyesight growing worse, followed by the eyesight of other cultures to which glasses spread but not beforehand. I don’t know much about the history of vision across time in different cultures, but something tells me that pattern wouldn’t show up if it could be assessed. In no small part, that intuition is driven by the relatively-brief window of historical time between when glasses were invented, and subsequently refined, produced in sufficient numbers, distributed globally, and today. A window of only about 700 years for all of that to happen and reduce selection pressures for vision isn’t a lot of time. Further, there seems to be evidence that myopia can develop rather rapidly in a population, sometimes as quick as a generation:

One of the clearest signs came from a 1969 study of Inuit people on the northern tip of Alaska whose lifestyle was changing2. Of adults who had grown up in isolated communities, only 2 of 131 had myopic eyes. But more than half of their children and grandchildren had the condition. 

That’s much too fast for a relaxation of selection pressures to be responsible for the change.

This brings us to the final hypothesis I wanted to cover today: an evolutionary mismatch hypothesis. In the event that modern environments differ in some key ways from the typical environments humans have faced ancestrally, it is possible that people will develop along an atypical path. In this case, the body is (metaphorically) expecting certain inputs during its development, and if they aren’t received things can go poorly. As a for instance, it has been suggested that people develop allergies, in part, as a result of improved hygiene: our immune systems are expecting a certain level of pathogen threat which, when not present, can result in our immune system attacking inappropriate targets, like pollen.

There does seem to be some promising evidence on this front for understanding human vision issues. A paper by Rose et al (2008) reports on myopia in two samples of similarly-aged Chinese children: 628 children living in Singapore and 124 living in Sydney. Of those living in Singapore, 29% appeared to display myopia, relative to only 3% of those living in Sydney. These dramatic differences in rates of myopia are all the stranger when you consider the rates of myopia in their parents were quite comparable. For the Sydney/Singapore samples, respectively, 32/29% of the children had no parent with myopia, 43/43% had one parent with myopia, and 25/28% had two parents with myopia. If myopia was simply the result of inherited genetic mutations, its frequencies between countries shouldn’t be as different as they are, disqualifying hypotheses one and three from above.

When examining what behavioral correlates of myopia existed between countries, several were statistically – but not practically – significant, including number of books read and hours spent on computers or watching TV. The only appreciable behavioral difference between the two samples was the number of hours the children tended to spend outdoors. In Sydney, the children spent an average of about 14 hours a week outside, compared to a mere 3 hours in Singapore. It might be the case, then, that the human eye requires exposure to certain kinds of stimulation provided by outdoor activities to develop properly, and some novel aspects of modern culture (like spending lots of time indoors in a school when children are young) reduce such exposure (which might also explain the aforementioned IQ correlation: smarter children may be sent to school earlier). If that were true, we should expect that providing children with more time outdoors when they are young is preventative against myopia, which it actually seems to be.

Natural light and no Wifi? Maybe I’ll just go blind instead…

It should always strike people as strange when key adaptive mechanisms appear to develop along an atypical path early in life that ultimately makes them worse at performing their function. An understanding of what types of biological explanations can account for these early maladaptive outcomes goes a long way in helping you understand where to begin your searches and what patterns of data to look out for.

References: Rose, K., Morgan, I., Smith, W., Burlutsky, G., Mitchell, P., & Saw, S. (2008). Myopia, lifestyle, and schooling in students of Chinese ehtnicity in Singapore and Sydney. Archives of Ophthalmology, 126, 527-530.

Why Do We Roast The Ones We Love?

One very interesting behavior that humans tend to engage in is murder. While we’re far from the only species that does this (as there are some very real advantages to killing members of your species – even kin – at times), it does tend to garner quite a bit of attention, and understandably so. One very interesting piece of information about this interesting behavior concerns motives; why people kill. If you were to hazard a guess as to some of the most common motives for murder, what would you suggest? Infidelity is a good one, as is murder resulting from other deliberate crimes, like when a robbery is resisted or witnesses are killed to reduce the probability of detection. Another major factor that many might not guess is minor slights or disagreements, such as one person stepping on another person’s foot by accident, followed by an insult (“watch where you’re going, asshole!”), which is responded to with an additional insult, and things kind of get out of hand until someone is dead (Daly & Wilson, 1988). Understanding why seemingly minor slights get blown so far out of proportion is a worthwhile matter in its own right. The short-version of the answer as to why it happens is that one’s social status (especially if you’re a male) can be determined, in large part, by whether other people know they can push you around. If I know you will tolerate negative behavior without fighting back, I might be encouraged to take advantage of you in more extreme ways more often. If others see you tolerating insults, they too may exploit you, knowing you won’t fight back. On the other hand, if I know you will respond to even slight threats with violence, I have a good reason to avoid inflicting costs on you. The more dangerous you are, the more people will avoid harming you.

“Anyone else have something to say about my shirt?! Didn’t think so…”

This is an important foundation for understanding why another facet of human behavior is strange (and, accordingly, interesting): friends frequently insult each other in a manner intended to be cordial. This behavior is exemplified well by the popular Comedy Central Roasts, where a number of comedians will get together to  publicly make fun of each other and their guest of honor. If memory serves, the (unofficial?) motto of these events is, “We only roast the ones we love,” which is intended to capture the idea that these insults are not intended to burn bridges or truly cause harm. They are insults born of affection, playful in nature. This is an important distinction because, as the murder statistics help demonstrate, strangers often do not tolerate these kinds of insults. If I were to go up to someone I didn’t know well (or knew well as an enemy) and started insulting their drug habits, dead loved ones, or even something as simple as their choice of dress, I could reasonably expect anything from hurt feelings to a murder. This raises an interesting series of mysteries surrounding the matter of why the stranger might want to kill me but my friends will laugh, as well as when my friends might be inclined to kill me as well.

Insults can be spoken in two primary manners: seriously and in jest. In the former case, harm is intended, while in the latter it often isn’t. As many people can attest to, however, the line between serious and jesting insults is not always as clear as we’d like. Despite our best intentions, ill-phrased or poorly-timed jokes can do harm in much the same way that a serious insult can. This suggests that the nature of the insults is similar between the two contexts. As the function of a serious insult between strangers would seem to be to threaten or lower the insulted target’s status, this is likely the same function of an insult made in jest between friends, though the degree of intended threat is lower in those contexts. The closest analogy that comes to mind is the difference between a serious fight and a friendly tussle, where the combatants either are, or are not, trying to inflict serious harm on each other. Just like play fighting, however, things sometimes go too far and people do get hurt. I think joking insults between friends go much the same way.

This raises another worthwhile question: as friends usually have a vested interest in defending each other from outside threats and being helpful, why would they then risk threatening the well-being of their allies through such insults? It would be strange if they were all risk and reward, so it would be up to us to explain what that reward is. There are a few explanations that come to mind, all of which focus on one crucial facet of friendships: they are dynamic. While friendships can be – and often are – stable over time, who you are friends with in general as well as the degree of that friendship changes over time. Given that friendships are important social resources that do shift, it’s important that people have reliable ways of assessing the strength of these relationships. If you are not assessing these relationships now and again, you might come to believe that your social ties are stronger than they actually are, which can be a problem when you find yourself in need of social support and realize that you don’t have it. Better to assess what kind of support you have before you actually need it so you can tailor your behavior more appropriately.

“You guys got my back, right?….Guys?….”

Insults between friends can help serve this relationship-monitoring function. As insults – even the joking kind – carry the potential to inflict costs on their target, the willingness of an individual to tolerate the insult – to endure those costs – can serve as a credible signal for friendship quality. After all, if I’m willing to endure the costs of being insulted by you without responding aggressively in turn, this likely means I value your friendship more than I dislike the costs being inflicted. Indeed, if these insults did not carry costs, they would not be reliable indications of friendship strength. Anyone could tolerate behavior that didn’t inflict costs to maintain a friendship, but not everyone will tolerate behaviors that do. This yields another prediction: the degree of friendship strength can also be assessed by the degree of insults willing to be tolerated. In other words, the more it takes to “go too far” when it comes to insults, the closer and stronger the friendship between two individuals. Conversely, if you were to make a joke about your friend that they become incredibly incensed over, this might result in your reevaluating the strength of that bond: if you thought the bond was stronger than it was, you might either take steps to remedy the cost you just inflicted and make the friendship stronger (if you value the person highly) or perhaps spend less time investing in the relationship, even to the point of walking away from it entirely (if you do not).

Another possible related function of these insults could be to ensure that your friends don’t start to think too highly of themselves. As mentioned previously, friendships are dynamic things based, in part, on what each party can offer to the other. If one friend begins to see major changes to their life in a positive direction, the other friend may no longer be able to offer the same value they did previously. To put that in a simple example, if two friends have long been poor, but one suddenly gets a new, high-paying job, the new status that job affords will allow that person to make friends he likely could not before. Because the job makes them more valuable to others, others will now be more inclined to be their friend. If the lower-status friend wishes to retain their friendship with the newly-employed one, they might use these insults to potentially undermine the confidence of their friend in a subtle way. It’s an indirect way of trying to ensure the high-status friend doesn’t begin to think he’s too good for his old friends.

Such a strategy could be risky, though. If the lower-status party can no longer offer the same value to the higher-status one, relative to their new options, that might also not be the time to test the willingness of the higher-status one to tolerate insults. At the same time, times of change are also precisely when the value of reassessing relationship strength can be at its highest. There’s less of a risk of a person abandoning a friendship when nothing has changed, relative to when it has. In either case, the assessment and management of social relationships is likely the key for understanding the tolerance of insults from friends and intolerance of them from strangers.

“Enjoy your new job, sellout. You used to be cool”

This analysis can speak to another interesting facet of insults as well: they’re directed towards the speaker at times, referred to self-deprecating humor when done in jest (and just self-deprecation when not). It might seem strange that people would insult themselves, as it would act to directly threaten their own status. That people do so with some regularity suggests there might be some underlying logic to these self-directed insults as well. One possibility is that these insults do what was just discussed: signal that one doesn’t hold themselves in high esteem and, accordingly, signal that one isn’t “too good” to be your friend. This seems like a profitable place from which to understand self-depreciating jokes. When such insults directed towards the self are not made in jest, they likely carry additional implications as well, such as that expectations should be set lower (e.g., “I’m really not able to do that”) or that one is in need of additional investment, relative to the joking kind. 

References: Daly, M. & Wilson, M. (1988). Homicide. Aldine De Gruyter: NY.

Semen Quality And The Menstrual Cycle

One lesson I always try to drive home in any psychology course I teach is that biology (and, by extension, psychology) is itself costly. The usual estimate on offer is that our brains consume about 20% of our daily caloric expenditure, despite making up a small portion of our bodily mass. That’s only the cost of running the brain, mind you; growing and developing it adds further metabolic costs into the mix. When you consider the extent of those costs over a lifetime, it becomes clear that – ideally – our psychology should only be expected to exist in an active state to the extent it offers adaptive benefits that tend to outweigh them. Importantly, we should also expect that cost/benefit analysis to be dynamic over time. If a component of our biology/psychology is useful during one point in our lives but not at another, we might predict that it would switch on or off accordingly. This line of thought could help explain why humans are prolific language learners early in life but struggle to learn a second language in their teens and beyond; a language-learning mechanism active during development it would be useful up to a certain age for learning a native tongue, but later becomes inactive when its services are no longer liable to required, so to speak (which they often wouldn’t be in an ancestral environment in which people didn’t travel far enough to encounter speakers of other languages).

“Good luck. Now get to walking!”

The two key points to take away from this idea, then, are (a) that biological systems tend to be costly and, because of that, (b) the amount of physiological investment in any one system should be doled out only to the extent it is likely to deliver adaptive benefits. With those two points as our theoretical framework, we can explain a lot about behavior in many different contexts. Consider mating as a for instance. Mating effort intended to attract and/or retain a partner is costly to engage in (in terms of time, resource invest, risk, and opportunity costs), so people should only be expected to put effort into the endeavor to the extent they view it as likely to produce benefits. As such, if you happen to be a hard “5″ on the mating market, it’s not worth your time pursuing a mate that’s a “9″ because you’re probably wasting your effort; similarly, you don’t want to pursue a “3″ if you can avoid it, because there are better options you might be able to achieve if you invest your efforts elsewhere.

Speaking of mating effort, this brings us to the research I wanted to discuss today. Sticking to mammals just for the sake of discussion, males of most species endure less obligate parenting costs than females. What this means is that if a copulation between a male and female results in conception, the female bears the brunt of the biological costs of reproduction. Many males will only provide some of the gametes required for reproduction, while the females must provide the egg, gestate the fetus, birth it, and nurse/care for it for some time. Because the required female investment is substantially larger, females tend to be more selective about which males they’re willing to mate with. That said, even though the male’s typical investment is far lower than the female’s, it’s still a metabolically-costly investment: the males need to generate the sperm and seminal fluid required for conception. Testicles need to be grown, resources need to be invested into sperm/semen production, and that fluid needs to be rationed out on a per-ejaculation basis (a drop may be too little, while a cup may be too much). Put simply, males cannot afford to just produce gallons of semen for fun; it should only be produced to the extent that the benefits outweigh the costs.

For this reason, you tend to see that male testicle size varies between species, contingent on the degree of sperm competition typically encountered. For those not familiar, sperm competition refers to the probability that a female will have sperm from more than one male in her reproductive tract at a time when she might conceive. In a concrete sense, this translates into a fertile female mating with two or more males during her fertile window. This creates a context that favors the evolution of greater male investment into sperm production mechanisms, as the more of your sperm are in the fertilization race, the greater your probability of beating the competition and reproducing. When sperm competition is rare (or absent), however, males need not invest as many resources into mechanisms for producing testes and they are, accordingly, smaller.

Find the sperm competition

This logic can be extended to matters other than sperm competition. Specifically, it can be applied to cases where a male is (metaphorically) deciding how much to invest into any given ejaculate, even if he’s the female’s only sexual partner. After all, if the female you’re mating with is unlikely to get pregnant at the time, whatever resources are being invested into an ejaculate are correspondingly more likely to represent wasted effort; a case where the male would be better off investing those resources to things other than his loins. What this means is that – in addition to between-species differences of average investment in sperm/semen production – there might also exist within-individual differences in the amount of resources devoted to a given ejaculate, contingent on the context. This idea falls under the lovely-sounding name, the theory of ejaculate economics. Put into a sentence, it is metabolically costly to “buy” ejaculates, so males shouldn’t be expected to invest in them irrespective of their adaptive value.

A prediction derived from this idea, then, is that males might invest more in semen quality when the opportunity to mate with a fertile female is presented, relative to when that same female is not as likely to conceive. This very prediction happens to have been recently examined by Jeannerat et al (2017). Their sample for this research consisted of 16 adult male horses and two adult females, each of which had been living in a single-sex barn. Over the course of seven weeks, the females were brought into a new building (one at a time) and the males were brought in to ostensibly mate with them (also one at a time). The males would be exposed to the female’s feces on the ground for 15 seconds (to potentially help them detect pheromones, we are told), after which the males and females were held about 2 meters from each other for 30 seconds. Finally, the males were led to a dummy they could mount (which had also been scented with the feces). The semen sample from that mount was then collected from the dummy and the dummy refreshed for the next male.

This experiment was repeated several times, such that each stallion eventually provided semen after exposure to each mare two or three times. The crucial manipulation, however, involved the mares: each male had provided a semen sample for each mare once when she was ovulating (estrous) and two to three times when she was not (dioestrous). These samples were then compared against each other, yielding a within-subjects analysis of semen quality.

The result suggested that the stallions could – to some degree – accurately detect the female’s ovulatory status: when exposed to estrous mares, the stallions were somewhat quicker to achieve erections, mount the dummy, and to ejaculate, demonstrating a consistent pattern of arousal. When the semen samples themselves were examined, another interesting set of patterns emerged: relative to dioestrous mares, when the stallions were exposed to estrous mares they left behind larger volumes of semen (43.6 mL vs 46.8 mL) and more motile sperm (a greater percentage of active, moving sperm; about 59 vs 66%). Moreover, after 48 hours, the sperm samples obtained from the stallions exposed to estrous mares showed less of a decline of viability (66% to 65%) relative to those obtained from dioestrous exposure (64% to 61%). The estrous sperm also showed reduced membrane degradation, relative to the dioestrous samples. By contrast, sperm count and velocity did not significantly differ between conditions.

“So what it was with a plastic collection pouch? I still had sex”

While these differences appear slight in the absolute sense, they are nevertheless fascinating as they suggest males were capable of (rather quickly) manipulating the quality of the ejaculate they provided from intercourse, depending on the fertility status of their mate. Again, this was a within-subjects design, meaning the males are being compared against themselves to help control for individual differences. The same male seemed to invest somewhat less in an ejaculate when the corresponding probability of successful fertilization was low.

Though there are many other questions to think about (such as whether males might also make long-term adjustments to semen characteristics depending on context, or what the presence of other males might do, to name a few), one that no doubt pops into the minds of people reading this is whether other species – namely, humans – do something similar. While it is certainly possible, from the present results we clearly cannot say; we’re not horses. An important point to note is that this ability to adjust semen properties depends (in part) on the male’s ability to accurately detect female fertility status. To the extent human males have access to reliable cues regarding fertility status (beyond obvious ones, like pregnancy or menstruation), it seems at least plausible that this might hold true for us as well. Certainly an interesting matter worth examining further.   

References: Jeannerat, E., Janett, F., Sieme, H., Wedekind, C., & Burger, D. (2017). Quality of seminal fluids varies with type of stimulus at ejaculation. Scientific Reports. 7, DOI: 10.1038/srep44339

 

The Connection Between Economics and Promiscuity

When it comes to mating, humans are a rather flexible species. In attempting to make sense of this variation, a natural starting point for many researchers is to try and tackle what might be seen as the largest question: why are some people more inclined to promiscuity or monogamy than others? Though many answers can be given to that question, a vital step in building towards a plausible and useful explanation of the variance is to consider the matter of function (as it always is). That is, we want to be asking ourselves the question, “what adaptive problems might be solved by people adopting long- or short-term mating strategies?” By providing answers to this question we can, in turn, develop expectations for what kind of psychological mechanisms exist to help solve these problems, explanations for how they could solve them, and then go examine the data more effectively for evidence of their presence or absence.

It will help until the research process is automated, anyway

The current research I wanted to talk about today begins to answer the question of function by considering (among other things) the matter of resource acquisition. Specifically, women face greater obligate biological costs when it comes to pregnancy than men. Because of this, men tend to be the more eager sex when it comes to mating and are often willing to invest resources to gain favor with potential mates (i.e., men are willing to give up resources for sex). Now, if you’re a woman, receiving this investment is an adaptive benefit, as it can be helpful in ensuring the survival and well-being of both yourself and your offspring. The question then becomes, “how can women most efficiently extract these resources from men?” As far as women are concerned, the best answer – in an ideal world – is to extract the maximum amount of investment from the maximum amount of men.

However, men have their own interests too; while they might be willing to pay-to-play, as it were, the amount they’re willing to give up depends on what they’re getting in return. What men are looking for (metaphorically or literally speaking) is what women have: a guarantee of sharing genes with their offspring. In other words, men are looking for paternity certainty. Having sex with a woman a single time increases the odds of being the father of one of her children, but only by a small amount. As such, men should be expected to prefer extended sexual access over limited access. Paternity confidence can also be reduced if a woman is having sex with one or more other men at the same time. This leads us to expect that men adjust their willingness to invest in women upwards if that investment can help them obtain one or both of those valued outcomes.

This line of reasoning lead the researchers to develop the following hypothesis: as female economic dependence on male investment increases, so too should anti-promiscuity moralization. That is, men and women should both increase their moral condemnation of short-term sex when male investment is more valuable to women. For women, this expectation arises because promiscuity threatens paternity confidence, and so their engaging in mating with multiple males should make it more difficult for them to obtain substantial male investment. Moreover, other women engaging in short-term sex similarly makes it more difficult for even monogamous women to demand male investment, and so would be condemned for their behavior as well. Conversely, since men value paternity certainty, they too should condemn promiscuity to a greater degree when their investment is more valuable, as they are effectively in a better position to bargain for what they want.

In sum, the expectation in the present study was that as female economic dependence increases, men and women should become more opposed to promiscuous mating.

“Wanted: Looking for paternity certainty. Will pay in cash”

This was tested in two different ways: in the first study, 656 US residents answered questions about their perceptions of female economic dependence on male investment in their social network, as well as their attitudes about promiscuity and promiscuous people. The correlation between the measures ended up being r = .28, which is a good proof of concept, though not a tremendous relationship (which is perhaps to be expected, given that multiple factors likely impact attitudes towards promiscuity). When economic dependence was placed into a regression to predict this sexual moralization, controlling for age, sex, religiosity, and conservatism in the first step, it was found that female economic dependence accounted for approximately 2% of the remaining variance in the wrongness of promiscuity ratings. That’s not nothing, to be sure, but it’s not terribly substantial either.

In the second study, 4,626 participants from across the country answered these same basic questions, along with additional questions, like their (and their partner’s) personal income. Again, there was a small correlation (r = .23) between female economic dependence and wrongness of promiscuity judgments. Also again, when entered into a regression, as before, an additional 2% of the variance in these wrongness judgments was predicted by economic dependence measures. However, this effect became more substantial when the analysis was conducted at the level of the states, rather than at the level of individuals. At the state level, the correlation between female economic dependence and attitudes towards promiscuity now rose to r = .66, with the dependence measure predicting 9% of the variance of promiscuity judgments in the regression with the other control factors.

Worth noting is that, though a women’s personal income was modestly predictive of her attitudes towards promiscuity, it was not as good of a predictor as her perception of the dependence of women she knows. There are two ways to explain this, though they are not mutually exclusive: first, it’s possible that women are adjusting their attitudes so as to avoid condemnation of others. If lots of women rely on this kind of investment, then she could be punished for being promiscuous even if it was in her personal interests. As such, she adopts anti-promiscuity attitudes as a way of avoiding punishment preemptively. The second explanation is that, given our social nature, our allies are important to us, and adjusting our moral attitudes so as to gain and maintain social support is also a viable strategy. It’s something of the other side of the same social support coin, and so both explanations can work together.

The dual-purpose marriage/friendship ring

Finally, I wanted to discuss a theoretical contradiction I find myself struggling to reconcile. Specifically, in the beginning of the paper, the authors mention that females will sometimes engage in promiscuous behavior in the service of obtaining resources from multiple males. A common example of this kind of behavior is prostitution, where a woman will engage in short-term intercourse with men in explicit exchange for money, though the strategy need not be that explicit or extreme. Rather than obtaining lots of investment from a single male, then, a viable female strategy should be to obtain several smaller investments from multiple males. Following this line of reasoning, then, we might end up predicting that female economic dependence on males might increase promiscuity and, accordingly, lower moral condemnation of it, at least in some scenarios.

If that were the case, the pattern of evidence we might predict is that, when female economic dependence is high, we should see attitudes towards promiscuity become more bi-modal, with some women more strongly disapproving of it while others become more strongly approving. As such, looking at the mean impact of these economic factors might be something of a wash (as they kind of were on the individual level). Instead, one might be interested in looking at the deviations from the mean instead, and see if those areas in which female economic dependence is the greatest show a larger standard deviation from the average moralization value than those in areas of lower dependence. Perhaps there are some theoretical reasons that this is implausible, but none are laid out in the paper.

References: Price, M., Pound, N., & Scott, I. (2014). Female economic dependence and the morality of promiscuity. Archives of Sexual Behavior, 43, 1289-1301.

Why Non-Violent Protests Work

It’s a classic saying: The pen is mightier than the sword. While this saying communicates some valuable information, it needs to be qualified in a significant way to be true. Specifically, in a one-on-one fight, the metaphorical pens do not beat swords. Indeed, as another classic saying goes: Don’t bring a knife to a gun fight. If knives aren’t advisable against guns, then pens are probably even less advisable. This raises the question as to how – and why – pens can triumph over swords in conflicts. These questions are particularly relevant, given some recent happenings in California at Berkeley where a protest against a speaking engagement by Milo Yiannopoulos took a turn for the violent. While those who initiated the violence might not have been students of the school, and while many people who were protesting might not engage in such violence themselves when the opportunity arises, there does appear to be a sentiment among some people who dislike Milo (like those leaving comments over on the Huffington Post piece) that such violence is to be expected, is understandable, and sometimes even morally justified or praiseworthy. The Berkeley riot was not the only such incident lately, either.

The Nazis shooting guns is a very important detail here

So let’s discuss why such violent behavior is often counterproductive for the swords in achieving their goals. Non-violent political movements, like those associated with leaders like Martin Luther King Jr. and Gandhi, appear to yield results, at least according to the only bit of data on the matter I’ve come across (for the link-shy: nonviolent campaigns combined complete and partial success rate was about 73%, while the comparable violent rate was about 33%). I even came across a documentary recently I intend to watch about a black man who purportedly got over 200 members of the KKK to leave the organization without force or the threat of it; he simply talked to them. That these nonviolent methods work at all seems rather unusual, at least if you were to frame it in terms of any other nonhuman species. Imagine, for instance, that a chimpanzee doesn’t like how he is being treated by the resident dominant male (who is physically aggressive), and so attempts to dissuade that individual from his behavior by nonviolently confronting him. No matter how many times the dominant male struck him, the protesting chimp would remain steadfastly nonviolent until he won over the other chimps in his group, and they all turned against the dominant male (or until the dominant male saw the error of his ways). As this would likely not work out for our nonviolent chimp, hopefully nonviolent protests are sounding a little stranger to you now; yet they often seem to work better than violence, at least for humans. We want to know why.

The answer to that question involves turning our attention back to the foundation of our moral sense: why do we perceive a dimension of right and wrong in the world in the first place? The short answer to this question, I think, is that when a dispute arises, those involved in the dispute find themselves in a state of transient need for social support (since numbers can decide the outcome of the conflict). Third parties (those not initially involved in the dispute) can increase their value as a social asset to one of the disputants by filling that need and assisting them in the fight against the rival. This allows third parties to leverage the transient needs of the disputants to build future alliances or defend existing allies. However, not all behaviors generate the same degree of need: the theft of $10 generates less need than a physical assault. Accordingly, our moral psychology represents a cognitive mechanism for determining what degree of need tends to be generated by behaviors in the interests of guiding where one’s support can best be invested (you can find the longer answer here). That’s not to say our moral sense will be the only input for deciding what side we eventually take – factors like kinship and interaction history matter too – but it’s an important part of the decision.

The applications of this idea to nonviolent protest ought to be fairly apparent: when property is destroyed, people are attacked, and the ability of regular citizens to go about their lives is disrupted by violent protests, this generates a need for social support on the part of those targeted or affected by the violence. It also generates worries in those who feel they might be targeted by similar groups in the future. So, while the protesters might be rioting because they feel they have important needs that aren’t being met (seeking to achieve them via violence, or the threat of it), third parties might come to view the damage inflicted by the protest as being more important or harmful (as they generate a larger, or more legitimate need). The net result of that violence is now that third parties side against the protesters, rather than with them. By contrast, a nonviolent protest does not create as large a need on the part of those it targets; it doesn’t destroy property or harm people. If the protesters have needs they want to see met and they aren’t inflicting costs on others, this can yield more support for the protester’s side.

I’m sure the owner of that car really had this coming…

This brings us to our third classic saying of the post: While I disagree with what you have to say, I will defend to the death your right to say it. Though such a sentiment might be seldom expressed these days, it highlights another important point: even if third parties agree with the grievances of the protesters (or, in this case, disagree with the behavior of the people being protested), the protesters can make themselves seem like suitably poor social assets by inflicting inappropriately-large costs (as disagreeing with someone generates less harm than stifling their speech through violence). Violence can alienate existing social support (since they don’t want to have to defend you from future revenge, as people who pick fights tend to initiate and perpetuate conflicts, rather than end them) and make enemies of allies (as the opposition now offers a better target of social investment, given their relative need). The answer as to why pens can beat swords, then, is not that pens are actually mightier (i.e., capable of inflicting greater costs), but rather that pens tend to be better at recruiting other swords to do their fighting for them (or, in more mild cases, pens can remove the social support from the swords, making them less dangerous). The pen doesn’t actually beat the sword; it’s the two or more swords the pen has persuaded to fight for it – and not the opposing sword – that do.

Appreciating the power of social support helps bolster our understanding of other possible interactions between pens and swords. For instance, when groups are small, swords will likely tend to be more powerful than pens, as large numbers of third parties aren’t around to be persuaded. This is why our nonviolent chimp example didn’t work well: chimps don’t reliably join disputes as third parties on the basis of behavior the way humans do. Without that third-party support, non-violence will fail. The corollary point here is that pens might find themselves in a bit of a bind when it comes to confrontations with other pens. Put in plain terms: nonviolence is a useful rallying cry for drawing social support if the other side of the dispute is being violent. If both sides abstain from violence, however, nonviolence per se no longer persuades people. You can’t convince someone to join your side in a dispute by pointing out something your side shares with the other. This should result in the expectation that people will frequently over-represent the violence of the opposition, perhaps even fabricating it completely, in the interests of persuading others. 

Yet another point that can be drawn from this analysis is that even “bad” ideas or groups (whether labeled as such because of moral or factual reasons) can recruit swords to their side if they are targeted by violence. Returning to the cases we began with – the riot at UC Berkeley and the incident where Richard Spencer got punched – if you hope to exterminate people who hold disagreeable views, then violence might seem like the answer. However, as we have seen, violence against others, even disagreeable others, who are not themselves behaving violently can rally support from third parties, as they might begin to worry that threats to free speech (or other important issues) are more harmful than the opinions and words we find disagreeable (again, hitting someone creates more need than talking does). On the other hand, if you hope to persuade people to join your side (or at least not join the opposition), you will need to engage with arguments and reasoning. Importantly, you need to treat those you hope to persuade as people and engage with the ideas and values they actually hold. If the goal in these disputes really is to make allies, you need to convince others that you have their best interests at heart. Calling those who disagree “baskets of deplorables,” suggesting they’re too stupid to understand the world, or anything to that extent doesn’t tend to win their hearts and minds. If anything, it sends a signal to them that you do not value them, giving them all the more reason to not spend their time helping you achieve your goals.  

“Huh; I guess I really am a moron and you’re right. Well done,” said no one, ever.

As a final matter, we could also discuss the idea that violence is useful at snuffing out threats preemptively. In other words, better to stop someone before they can try and attack you, rather than after their knife is already in your back. There are several reasons preemptive defense is just as suspect, so let’s run through a few: first, there are different legal penalties for acts like murder and attempted murder, as attempted – but incomplete acts – generate less needs than completed ones. As such, they garner less social support. Second, absent very strong evidence that the people targeted for violence would have eventually become violent, the preemptive attacks will not look defensive; they will simply look aggressive, returning to the initial problems violent protests face. Relatedly, it is unlikely to ever make allies of enemies; if anything, it will make deeper enemies of existing ones and their allies. Remember: when you hurt someone, you indirectly inflict costs on their friends, families, and other relations as well. Finally, some people will likely develop reasonable concerns about the probability of being attacked for holding other opinions or engaging in behaviors people find unpleasant or dangerous. With speech already being equated to violence among certain groups, this concern doesn’t seem unfounded. 

In the interests of persuading others – actors and third parties alike – nonviolence is usually the better first step. However, nonviolence alone is not enough, especially if your opposition is nonviolent as well. Not being violent does not mean you’ve already won the dispute; just that you haven’t lost it. It is at that point you need to persuade others that your needs are legitimate, your demands reasonable, and your position in their interests as well, all while your opposition attempts to be persuasive themselves. It’s not an easy task, to be sure, and it’s one many of us are worse at then we’d like to think; it’s just the best way forward.

The Adaptive Significance Of Priming

One of the more common words you’ll come across in the psychological literature is priming, which is defined as an instance where exposure to one stimulus influences the reaction to a subsequent one. There are plenty of examples one might think of to demonstrate this effect, one of which might be if you were to ask participants to tell you whether a string of letters they see pop up on a screen is a word or a non-word. They would be quicker to respond to the word “nurse” if it were preceded by the prime of “doctor” relative to being preceded by “chair,” owing to the relative association (or lack thereof) between the words. While a great deal of psychological literature deals with priming, very few papers I have come across actually attempt to give some kind of adaptive, functional account of what priming is and, accordingly, why they should expect it to behave the way it does. Because of that absence of theoretical grounding, some research that utilizes priming ends up generating some hypotheses that aren’t just strange; they’re biologically implausible. 

Pictured: Something strange, but at least biological plausible

To give a more concrete sense of what I mean, I wanted to briefly summarize some of that peculiar research using priming that I’ve covered before. In this case, the research either focuses on how priming can affect perceptions about the world or how priming can affect people’s behavior. These lines of inquiry often seem to try and demonstrate how people are biased, inaccurate, or otherwise easily manipulated by seemingly-minor environmental influences. To see what I mean, let’s consider some research findings on both fronts. In terms of perceptions about the world, a few findings are highlighted in this piece, including the prospect that holding a warm drink (instead of a cold one) can lead you judge other people as more caring and generous; a finding that falls under the umbrella of embodied cognition. Why would such a finding arise? If I understand correctly, the line of thought is that holding a warm drink activates some part of your brain that holds the concept “warm”; as that concept is tied indirectly to personality (e.g., “He’s a really warm and friendly person”), you end up thinking the person is nicer than you otherwise would. Warm drinks prime the concept of emotional warmth.

It doesn’t take much thinking about this explanation to see why it seems wrong: a mind structured in such a way would be making a mistake about the world. Specifically, because holding a warm object in your hand should have no effect on the personality and behavior of someone else, if you use that temperature information to influence your judgments, you will be more likely to misjudge the probable intentions of others. If you’re not nice, but I think you are (or at least you’re not as nice as I think you are), I will behave in sub-optimal ways, perhaps by putting more trust in you than I should or generating other expectations of you that won’t be fulfilled. Because there are real costs to being wrong about others – as it opens you up to risks of exploitation, for instance – a cognitive system wired this way should be outperformed by one which ignores more irrelevant information.

Other such examples of the effects of priming posit something similar, except on a behavioral level instead of a perceptual one. For instance, research on stereotype threat suggests that if you remind women of their gender before a math test (in other words, you’re priming gender), they will tend to perform worse than women who were not primed because the concept of “woman” is related to stereotypes of “being worse at a math.” This should be maladaptive for precisely the same reason that the perceptual variety is: actively making yourself worse at a task than you actually are will tend to carry costs. To the extent this effect ostensibly runs in the opposite direction – a case where someone gets better at a task because of a prime, as is the case in the work on power poses – one would wonder why an individual should wait for a prime rather than just get on with the task at hand. Now sure, these effects don’t replicate well and probably aren’t real (see stereotype threat, power poses, and elderly prime effects on walking speed), but that they would even be proposed in the first place is indicative of a problem in the way people think about psychology. They seem like ideas that couldn’t even possibly be correct, given what they would imply about the probable fitness costs to their bearers. Positing maladaptive psychological mechanisms seems rather perverse.

Now I suspect some might object at this point and remind me that not everything our brains do is adaptive. In fact, priming might simply just be an occasionally maladaptive byproduct of activating certain portions of our brain by proximity. This is referred to as spreading activation and it might just be an unfortunate byproduct of brain wiring. “Sure,” you might say, “this kind of spreading activation isn’t adaptive, but it’s just a function of how the brain gets wired up. Our brains can’t help it.” Well, as it turns out, it seems they certainly can.

“Don’t give me that look; you knew better!”

This brings me to some research on memory and priming by Klein et al (2002). These researchers begin with their adaptive framework for priming, suggesting that priming reflects a feature of our cognitive systems – rather than a byproduct – that helps speed up the delivery of appropriate information. In short, priming represents something of a search engine that uses one’s present state to try and predict what information will be needed in the near future. It is crucial to emphasize the word “appropriate” in that hypothesis: the benefits to accessing information stored in our memories, for instance, is to help guide our current behavior. As there many more ways of guiding your behavior towards some maladaptive end, rather than an adaptive one, information stored in memory needs to be accessed selectively. If you spend too much time accessing irrelevant or distracting information, the function of the priming itself – to deliver relevant information quickly – would be thwarted. To put that into a simple example, if you’re trying to quickly solve a problem related to whether you should trust someone, accessing information about what you had for breakfast that morning will not only fail to help you, but it will actively slow your completion of the task down. You’d be wasting time processing irrelevant information.

To demonstrate this point, Klein et al (2002) decided to look at trait judgments: essentially asking people a question like, “how well does the word ‘kind’ describe [you/someone else]?” Without going into too much detail on the matter, our brains seem to store information relevant to these tasks in two different formats: in a summary form and an episodic form. This means one memory system contains information about particular behavioral instances (e.g., a time someone was kind or mean) while another derives summaries of that behavior (e.g., that person, overall, is kind or mean). Broadly speaking, these different memory systems exist owing to a cognitive trade-off between speed and accuracy in judgments: if you want to know how to behave towards someone, it’s quicker to consult the summary information than process every individual memory of their behaviors. However, the summary information tends to be less complete and accurate than the sum of the individual memories. That is, knowing that someone is “often nice” doesn’t give you insight into the conditions during which they are mean. 

As such, if someone was trying to make a judgment about whether you were nice, if they have a summary of “often nice,” they don’t need to spend time consulting memories of every nice thing you’ve done; that would be redundant processing. Instead, they would want to selectively consult the information about times you are not nice, as this would help them figure out the boundary conditions of their judgment; when the “often nice” label doesn’t apply. This lead Klein et al (2002) to the following prediction: retrieving a trait summary of a person should prime trait-inconsistent episodes from memory, rather than trait-consistent ones. In short, priming effects ought to be functionally specific.

“The cat is usually friendly, except for those times you shaved him”

And that is exactly what they found: when participants were asked to judge whether a trait described them (or their mother), they were quicker to subsequently recall a time they (or their mother) behaved in an inconsistent manner. To put that in context, if participants were asked whether the word “polite” described them, they would be quicker to recall a specific instance they were rude, relative to a time they were polite. Moreover, just being asking to define the terms (e.g., rude or polite) didn’t appear to prime trait-consistent episodes in memory either: participants were not quicker to recall a time they were polite after having defined the term. This would be a function of the fact that defining a term does not require you to make a trait judgment about it, so episodic memories wouldn’t be relevant information.

These results are important because if priming were truly just a byproduct of spreading neural activation, then trait-judgments (Are you kind?) should prime trait-consistent episodes (a time you were kind); they just don’t seem to do that. As such, we could conclude that priming does not appear to just be a byproduct of neural activation. If priming isn’t just a biological necessity, then, studies which make use of this paradigm would have to better justify their expectations. If it’s not justifiable to expect indiscriminate neural activation, researchers would need to put in more time to explain and understand the particular patterns of priming they find. Ideally they would do this advance of conducting the research (as Klein et al did), as that would likely save people a lot of time publishing papers on priming that subsequently fail to replicate.  

References: Klein, S., Cosmides, L., Tooby, J., & Chance, S. (2002). Decisions and the evolution of memory: multiple systems, multiple functions. Psychological Review, 109, 306-329.

Overperception Of Sexual Interest Or Overeager Researchers?

Though I don’t make a habit of watching many shows, I do often catch some funny clips of them that have been posted online. One that I saw semi-recently (which I feel relates to the present post) is a clip from Portlandia. In this video, people are writing a magazine issue about a man living a life that embodies manhood. In this case, they select a man who used to work at an office, but then left his job and now makes furniture. While everyone is really impressed with the idea, it eventually turns out that the man in question does make furniture…but it’s terrible. Faced with the revelation that the man’s work isn’t good – that it probably wasn’t worth leaving his job to do something he’s bad at – the people in question aren’t impressed by his over-confidence in pursuing his furniture work. They don’t seem to find him more attractive because he was overconfident; quite the opposite in fact. The key determent of his attractiveness was the actual quality of his work. In other words, since he couldn’t back up his confidence with his efforts, the ratings of his attractiveness appeared to drop precipitously.

It might not be comfortable, but at least it’s hand-made

What we can learn from an example like this is that something like overconfidence per se – being more confident than one should be and behaving in ways one rightfully shouldn’t because of it – doesn’t appear to be impressive to potential mates. As such, we might expect that people who pursue activities they aren’t well suited for tend to do worse in the mating domain than those who are able to exist within a niche they more suitably fill: if you can’t cut it as a craftsman, better to keep that steady, yet less-interesting office job. This is largely a factor of the overconfident investing their time and effort into pursuits that do not yield positive benefits for them or others. You can think of it like playing the lottery, in a sense: if you are overly-confident that you’ll win the lottery, you might incorrectly invest money into lottery tickets that you could otherwise spend on pursuits that don’t amount to lighting it on fire.

This is likely why the research on the (over)perception of sexual intent turns out the way it does. I’ve written about the topic before, but to give you a quick overview of the main points: researchers have uncovered that men tend to perceive more sexual interest in women than women themselves report having. To put that in a simple example, if you were to ask a woman, “given you were holding a man’s hand, how sexually interested in him are you?” you’ll tend to get a different answer than if you ask a man, “given that a woman was holding your hand, how sexually interested do you think she is in you?” In particular, men tend to think behaviors like hand-holding signal more sexual intent than women report. These kinds of results have been chalked up to men overperceiving sexual intent, but more recent research puts a different spin on the answers: specifically, if you were to ask a woman, “given that another woman (who is not you) is holding a man’s hand, how sexually interested in him do you think she is?” the answers from the women now align with those of the men. Women (as well as men) seem to believe that other women will underreport their sexual intent, while believing their own self-reports are accurate. Taken together, then, both men and women seem to perceive more sexual intent in a woman’s behavior than the woman herself reports. Rather than everyone else overperceiving sexual intent, it seems a bit more probable that women themselves tend to underreport their own sexual intent. In a sentence, women might play a little coy, rather than everyone else in the world being wrong about them.

Today, I wanted to talk about a very recent paper (Murray et al, 2017) by some of the researchers who seem to favor the overperception hypothesis. That is, they seem to suggest that women honestly and accurately report their own sexual interest, but everyone else happens to perceive it incorrectly. In particular, their paper represents an attempt to respond to the point that women overperceive the sexual intent of other women as well. At the outset, I will say that I find the title of their research rather peculiar and their interpretation of the data rather strange (points I’ll get to below). Indeed, I found both things so strange that I had to ask around a little first before I stared writing this post to ensure that I wasn’t misreading something, as I know smart people wrote the paper in question and the issues seemed rather glaring to me (and if a number of smart people seem to be mistaken, I wanted to make sure the error wasn’t simply something on my end first). So let’s get into what was done in the paper and why I think there are some big issues.

“…Am I sure I’m not the crazy one here, because this seems real strange”

Starting out with what was done, Murray et al (2017) collected data from 414 heterosexual women online. These women answered questions about 15 different behaviors which might signal romantic interest. They were first asked these questions about themselves, and then about other women. So, for instance, a woman might be asked, “If you held hands with a man, how likely is it you intend to have sex with him?” They would then be asked the same hand-holding question, but about other women: “If a woman (who is not you) held hands with a man, how likely is it that she would…” and then end with something along the lines of, “say she wants to have sex with him,” or “actually want to have a sex with him.” They were trying to tap this difference between the perceptions of “what women will say” and “what women actually want” responses. They also wanted to see what happened when you ask the “say” or “want” question first.

Crucially, the previous research these authors are responding to found that both men and women tend to report that, in general, women tend to want more than they say. The present research was only looking at women, but it found that same pattern: regardless of whether you ask the “say” or “want” questions first, women seem to think that other women will say they are less interested than they actually are. In short, women believe other women to be at least somewhat coy. In that sense, these results are a direct replication of the previous findings.

One of the things I find strange about the paper, then, is the title: “A Preregistered Study of Competing Predictions Suggests That Men Do Overestimate Women’s Sexual Intent.” Since this study was only looking at women, the use of “men” in the title seems poorly thought out. I assume the intentions of the authors were to say that these results are consistent with the idea that men also overperceive, but even in that case it really ought to say “People Overestimate,” rather than “Men Do.” I earnestly can’t think of a reason to single out the male gender in the title other than the possibility that the authors seem to have forgotten they were measuring something other than what they actually wanted to. That is, they wanted their results to speak to the idea that male perceptions are biased upwards (in order support their own, prior work), but they seem to be a bit overeager to do so and jumped the gun.

“Well women are basically men anyway, right? Close enough”

Another point I find rather curious from the paper – some data the authors highlight – is that the women’s responses did depend (somewhat) on whether you ask the “say” or “want” questions first. Specifically, the responses to both the “say” and “want” scales are a little lower when the “want” question is asked first. However, the relative pattern of the data – the effect of perceived coyness – exists regardless of the order. I’ve attached a slightly-modified version of their graph below so you can see what their results look like.

What this suggests to me is that something of an anchoring effect exists, whereby the question order might affect how people interpret the values on the scale of sexual intent (which goes from 1 to 7). What it does not suggest to me is what Murray et al (2017) claim it does:

These results support the hypothesis that women’s differential responses to the “say” and “want” questions in Perilloux and Kurzban’s study were driven by question-order effects and language conventions, rather than by women’s chronic underreporting of their sexual intentions.”

As far as I can tell, they do nothing of the sort. Their results – to reiterate – are effectively direct replications of what Perilloux & Kurzban found. Regardless of the order in which you ask the questions, women believed other women wanted more than they would let on. How that is supposed to imply that the previously (and presently) observed effects are due to questioning ordering are beyond me. To convince me this was simply an order effect, data would need to be presented that either (a) showed the effect goes away when the order of the questions is changed or (b) showed the effect changes direction when the question order is changed. Since neither of those things happened, I’m hard pressed to see how the results can be chalked up to order effects.

For whatever reason, Murray et al (2017) seem to make a strange contrast on that front:

We predicted that responses to the “say” and “want” questions would be equivalent when they were asked first, whereas Perilloux and Kurzban confirmed their prediction that ratings for the “want” question would be higher than ratings for the “say” question regardless of the order of the questions”

Rather than being competing hypotheses, these two seem like hypotheses that could both be true: you could see that people interpret the values on the scales differently, depending on which question you ask first while also predicting that the ratings for “want” questions will be higher than those for “say” questions, regardless of the order. Basically, I have no idea why the word “whereas” was inserted into that passage, as if to suggest both of those things could not be true (or false) at the same time (I also have no idea why the word “competing” was inserted into the title of their paper, as it seems equally inappropriate there as the word “men”). Both of those hypotheses clearly can both be true and, indeed, seem to be if these results are taken at face value.

“They predict this dress contains the color black, whereas we predict it contains white”

To sum up, the present research by Murray et al (2017) doesn’t seem to suggest that women (and, even though they didn’t look at them in this particular study, men) overperceive other women’s sexual intentions. If anything, it suggests the opposite. Indeed, as their supplementary file points out, “…across both experimental conditions women reported their own sexual intentions to be significantly lower than both what other women say and what they actually want,” and, “…it seems that when reporting on their own behavior, the most common responses for acting either less or more interested are either never engaging in this behavior or sometimes doing so, whereas women seem to believe that other women most commonly engage in both behaviors some of the time.”

So, not only do women believe that other women (who aren’t them) engage in this coy behavior more often than they themselves do (which would be impossible, as not everyone can think that about everyone else and be right), but women also even admit to, at least sometimes, acting less interested than they actually are. When women are actually reporting that, “Yes, I have sometimes underreported my sexual interest,” well, that seems to make the underreporting hypothesis sound a bit more plausible. The underreporting hypothesis would also be consistent with the data that finds women tend to underreport their number of sexual partners when they think others might see that report or lies will not be discovered; by contrast, male reports of partner numbers are more consistent (Alexander & Fisher, 2003).

Perhaps the great irony here, then, is the Murray et al (2017) might have been a little overeager to interpret their results in a certain fashion, and so end up misinterpreting their study as speaking to men (when it only looks at women) and their hypothesis as being a competing one (when it is not). There are costs to being overeager, just as there are costs to being overconfident; better to stick with appropriate eagerness or confidence to avoid those pitfalls. 

References: Alexander MG, & Fisher TD (2003). Truth and consequences: using the bogus pipeline to examine sex differences in self-reported sexuality. Journal of sex research, 40 (1), 27-35

Murray, D., Murphy, S., von Hippel, W., Trivers, R., & Haselton, M. (2017). A preregistered study of competing predictions suggests that men do overestimate women’s sexual intent. Psychological Science. 

 

Intergenerational Epigenetics And You

Today I wanted to cover a theoretical matter I’ve discussed before but apparently not on this site: the idea of epigenetic intergenerational transmission. In brief, epigenetics refers to chemical markers attached to your DNA that regulate how it’s expressed and regulated without changing the DNA itself. You could imagine your DNA as a book full of information and each cell in your body contains the same book. However, not every cell expressed the full genome; each cell only expresses part of it (which is why skin cells are different from muscle cells, for instance). The epigenetic portion, then, could be thought of as black tape placed over certain passages in the books so they are not read. As this tape is added or removed by environmental influences, different portions of the DNA will become active. From what I understand about how this works (which is admittedly very little at this juncture), usually these markers are not passed onto offspring from parents. The life experiences of your parents, in other words, will not be passed onto you via epigenetics. However, there has been some talk lately of people hypothesizing that not only are these changes occasionally (perhaps regularly?) passed on from parents to offspring; the implication seems to be present that they also might be passed on in an adaptive fashion. In short, organisms might adapt to their environment not just through genetic factors, but also through epigenetic ones.  

Who would have guessed Lamarckian evolution was still alive?

One of the examples given in the target article on the subject concerns periods of feast and famine. While rare in most first-world nations these days, these events probably used to be more recurrent features of our evolutionary history. The example there involves the following context: during some years in early 1900 Sweden food was abundant, while during other years it was scarce. Boys who were hitting puberty just at the time of a feast season tended to have grandchildren who died six years earlier than the grandchildren of boys who have experienced famine season during the same developmental window. The causes of death, we are told, often involving diabetes. Another case involves the children of smokers: men who smoked right before puberty tended to have children who were fatter, on average, than fathers who smoked habitually but didn’t start until after puberty . The speculation, in this case, is that development was in some way affected in a permanent fashion by food availability (or smoking) during a critical window of development, and those developmental changes were passed onto their sons and the sons of their sons.

As I read about these examples, there were a few things that stuck out to me as rather strange. First, it seems odd that no mention was made of daughters or granddaughters in that case, whereas in the food example there wasn’t any mention of the in-between male generation (they only mentioned grandfathers and grandsons there; not fathers). Perhaps there’s more to the data that is let on there but – in the event that no effects were found for fathers or daughters or any kind – it is also possible that a single data set might have been sliced up into a number of different pieces until the researchers found something worth talking about (e.g., didn’t find an effect in general? Try breaking the data down by gender and testing again). Now that might or might not be the case here, but as we’ve learned from the replication troubles in psychology, one way of increasing your false-positive rate is to divide your sample into a number of different subgroups. For the sake of this post, I’m going to assume that is not the case and treat the data as representing something real, rather than a statistical fluke.   

Assuming this isn’t just a false-positive, there are two issues with the examples as I see them. I’m going to focus predominately on the food example to highlight these issues: first, passing on such epigenetic changes seems maladaptive and, second, the story behind it seems implausible. Let’s take the issues in turn.

To understand why this kind of inter-generational epigenetic transmission seems maladaptive, consider two hypothetical children born one year apart (in, say, the years 1900 and 1901). At the time the first child’s father was hitting puberty, there was a temporary famine taking place and food was scarce; at the time of the second child, the famine had passed and food was abundant. According to the logic laid out, we should expect that (a) both children will have their genetic expression altered due to the epigenetic markers passed down by their parents, affecting their long-term development, and (b) the children will, in turn, pass those markers on to their own children, and their children’s children (and so on).

The big Thanksgiving dinner that gave your grandson diabetes

The problems here should become apparent quickly enough. First, let’s begin by assuming these epigenetic changes are adaptive: they are passed on because they are reproductively useful at helping a child develop appropriately. Specifically, a famine or feast at or around the time of puberty would need to be a reliable cue as to the type of environments their children could expect to encounter. If a child is going to face shortages of food, they might want to develop in a different manner than if they’re expecting food to be abundant.

Now that sounds well and good, but in our example these two children were born just a year apart and, as such, should be expected to face (broadly) the same environment, at least with respect to food availability (since feast and famines tends to be more global). Clearly, if the children were adopting different developmental plans in response to that feast of famine, both of them (plan A affected by the famine and plan B not so affected) cannot be adaptive. Specifically, if this epigenetic inheritance is trying to anticipate children’s future conditions by those present around the time of their father’s puberty, at least one of the children’s developmental plans will be anticipating the wrong set of conditions. That said, both developmental plans could be wrong, and conditions could look different than either anticipated. Trying to anticipate the future conditions one will encounter over their lifespan (and over their children’s and grandchild’s lifespan) using only information from the brief window of time around puberty seems like a plan doomed for failure, or at least suboptimal results.

A second problem arises because these changes are hypothesized to be intergenerational: capable of transmission across multiple generations. If that is the case, why on Earth would the researchers in this study pay any mind to the conditions the grandparents were facing around the time of puberty per se? Shouldn’t we be more concerned with the conditions being faced a number of generations backs, rather than the more immediate ones? To phrase this in terms of a chicken/egg problem, shouldn’t the grandparents in question have inherited epigenetic markers of their own from their grandparents, and so on down the line? If that were the case, the conditions they were facing around their puberty would either be irrelevant (because they already inherited such markers from their own parents) or would have altered the epigenetic markers as well.

If we opt for the former possibility, than studying grandparent’s puberty conditions shouldn’t be too impactful. However, if we opt for the latter possibility, we are again left in a bit of a theoretical bind: if the conditions faced by the grandparents altered their epigenetic markers, shouldn’t those same markers also have been altered by the parent’s experiences, and their grandson’s experiences as well? If they are being altered by the environment each generation, then they are poor candidates for intergenerational transmission (just as DNA that was constantly mutating would be). There is our dilemma, then: if epigenetics change across one’s lifespan, they are unlikely candidates for transmission between generations; if epigenetic changes can be passed down across generations stably, why look at the specific period pre-puberty for grandparents? Shouldn’t we be concerned with their grandparents, and so on down the lines?

“Oh no you don’t; you’re not pinning this one all on me”

Now, to be clear, a famine around the time of conception could affect development in other, more mundane ways. If a child isn’t receiving adequate nutrition at the time they are growing, then it is likely certain parts of their developing body will not grow as they otherwise would. When you don’t have enough calories to support your full development, trade-offs need to be made, just like if you don’t have enough money to buy everything you want at the store you have to pass up on some items to afford others. Those kinds of developmental outcomes can certainly have downstream effects on future generations through behavior, but they don’t seem like the kind of changes that could be passed on the way genetic material can. The same can be said about the smoking example provided as well: people who smoked during critical developmental windows could do damage to their own development, which in turn impacts the quality of the offspring they produce, but that’s not like genetic transmission at all. It would be no more surprising than finding out that parents exposed to radioactive waste tend to have children of a different quality than those not so exposed.

To the extent that these intergenerational changes are real and not just statistical oddities, it doesn’t seem likely that they could be adaptive; they would instead likely reflect developmental errors. Basically, the matter comes down to the following question: are the environmental conditions surrounding a particular developmental window good indicators of future conditions to the point you’d want to not only focus your own development around them, but also the development of your children and their children in turn? To me, the answer seems like a resounding, ‘”No, and that seems like a prime example of developmental rigidity, rather than plasticity.” Such a plan would not allow offspring to meet the demands of their unique environments particularly well. I’m not hopeful that this kind of thinking will lead to any revolutions in evolutionary theory, but I’m always willing to be proven wrong if the right data comes up. 

Mistreated Children Misbehaving

None of us are conceived or born as full adults; we all need to grow and develop from single cells to fully-formed adults. Unfortunately – for the sake of development, anyway – the future world you will find yourself in is not always predictable, which makes development a tricky matter at times. While there are often regularities in the broader environment (such as the presence or absence of sunlight, for instance), not every individual will inhabit the same environment or, more precisely, the same place in their environment. Consider two adult males, one of whom is six-feet tall and 230 pounds of muscle, and the other being five-feet tall and 110 pounds. While the dichotomy here is stark, it serves to make a simple point: if both of these males developed in a psychological manner that led them to pursue precisely the same strategies in life – in this case, say, one involving aggressive contests for access to females – it is quite likely that the weaker male will lose out to the stronger one most (if not all) of the time. As such, in order to be more-consistently adaptive, development must be something of a fluid process that helps tailor an individual’s psychology to the unique positions they find themselves in within a particular environment. Thus, if an organism is able to use some cues within their environment to predict their likely place in it in the future (in this case, whether they would grow large or small), their development could be altered to encourage their pursuit of alternate routes to eventual reproductive success. 

Because pretending you’re cut out for that kind of life will only make it worse

Let’s take that initial example and adapt it to a new context: rather than trying to predict whether one will grow up weak or strong, a child is trying to predict the probability of receiving parental investment in the future. If parental investment is unlikely to be forthcoming, children may need to take a different approach to their development to help secure the needed resources on their own, sometimes requiring their undertaking risky behaviors; by contrast, those children who are likely to receive consistent investment might be relatively less-inclined to take such risky and costly matters into their own hands, as the risk vs. reward calculations don’t favor such behavior. Placed in an understandable analogy, a child who estimates they won’t be receiving much investment from their parents might forgo a college education (and, indeed, even much of a high-school one) because they need to work to make ends meet. When you’re concerned about where your next meal is coming from there’s less time in your schedule for studying and taking out loans to not be working for four years. By contrast, the child from a richer family has the luxury of pursuing an education likely to produce greater future rewards because certain obstacles have been removed from their path.

Now obviously going to college is not something that humans have psychological adaptations for – it wasn’t a recurrent feature of our evolutionary history as a species – but there are cognitive systems we might expect to follow different developmental trajectories contingent on such estimations of one’s likely place in the environment; these could include systems judging the relative attractiveness of short- vs long-term rewards, willingness to take risks, pursuit of aggressive resolutions to conflicts, and so on. If the future is uncertain, saving for it makes less than taking a smaller reward in the present; if you lack social or financial support, being willing to fight to defend what little you do have might sound more appealing (as losing that little bit is more impactful when you won’t have anything left). The questions of interest thus becomes, “what cues in the environment might a developing child use to determine what their future will look like?” This brings us to the current paper by Abajobir et al (2016).

One potential cue might be your experiences with maltreatment while growing up, specifically at the hands of your caregivers. Though Abajobir et al (2016) don’t make the argument I’ve been sketching out explicitly, that seems to be the direction their research takes. They seem to reason (implicitly) that parental mistreatment should be a reliable cue to the future conditions you’re liable to encounter and, accordingly, one that children could use to alter their development. For instance, abusive or neglectful parents might lead to children adopting faster life history strategies involving risk-taking, delinquency, and violence themselves (or, if they’re going the maladaptive explanatory route, the failure of parents to provide supporting environments could in some way hinder development from proceeding as it usually would, in a similar fashion to not having enough food growing up might lead to one being shorter as an adult. I don’t know which line the authors would favor from their paper). That said, there is a healthy (and convincing) literature consistent with the hypothesis that parental behavior per se is not the cause of these developmental outcomes (Harris, 2009), but rather that it simply co-occurs with them. Specifically, abusive parents might be genetically different from non-abusive ones and those tendencies could get passed onto the children, accounting for the correlation. Alternatively, parents that maltreat their children might just happen to go together with children having peer groups growing up more prone to violence and delinquency themselves. Both are caused by other third variables.

Your personality usually can’t be blamed on them; you’re you all on your own

Whatever the nature of that correlation, Abajobir et al (2016) sought to use parental maltreatment from ages 0 to 14 as a predictor of later delinquent behaviors in the children by age 21. To do so, they used a prospective cohort of children and their mothers visiting a hospital between 1981-83. The cohort was then tracked for substantiated cases of child maltreatment reported to government agencies up to age 14, and at age 21 the children themselves were surveyed (the mothers being surveyed at several points throughout that time). Out of the 7200 initial participants, 3800 completed the 21-year follow up. At that follow up point, the children were asked questions concerning how often they did things like get excessively drunk, use recreational drugs, break the law, lie, cheat, steal, destroy the property of others, or fail to pay their debts. The mothers were also surveyed on matters concerning their age when they got pregnant, their arrest records, martial stability, and the amount of supervision they gave their children (all of these factors, unsurprisingly, predicting whether or not people continued on in the study for its full duration).

In total, of the 512 eventual cases of reported child maltreatment, only 172 remained in the sample at the 21-year follow up. As one might expect, maternal factors like her education status, arrest record, economic status, and unstable marriages all predicted increased likelihood of eventual child maltreatment. Further, of the 3800 participants, only 161 of them met the criteria for delinquency at 21 years. All of the previous maternal factors predicted delinquency as well: mothers who were arrested, got pregnant earlier, had unstable marriages, less education, and less money tended to produce more delinquent offspring. Adjusting for the maternal factors, however, it was reported that childhood maltreatment still predicted delinquency, but only for the male children. Specifically, maltreatment in males was associated with approximately 2-to-3.5 times as much delinquency as the non-maltreated males. For female offspring, there didn’t seem to be any notable correlation.

Now, as I mentioned, there are some genetic confounds here. It seems probable that parents who maltreat their children are, in some very real sense, different than parents who do not, and those tendencies can be inherited. This also doesn’t necessarily point a causal finger directly at parents, as it is also likely that maltreatment correlates with other social factors, like the peer group a child is liable to have or the neighborhoods they grow up in. The authors also mention that it is possible their measures of delinquency might not capture whatever effects childhood maltreatment (or its correlates) have on females, and that’s the point I wanted to wrap up discussing. To really put these findings on context, we would need to understand what adaptive role these delinquent behaviors – or rather the psychological mechanisms underlying them – have. For instance, frequent recreational drug use and problems fulfilling financial obligations might both signal that the person in question favors short-term rewards over long-term ones; frequent trouble with the law or destroying other people’s property could signal something about how the individual in question competes for social status. Maltreatment does seem to predict (even if it might not cause) different developmental courses, perhaps reflecting an active adjustment of development to deal with local environmental demands.

 The kids at school will all think you’re such a badass for this one

As we reviewed in the initial example, however, the same strategies will not always work equally well for every person. Those who are physically weaker are less likely to successfully enact aggressive strategies, all else being equal, for reasons which should be clear. Accordingly, we might expect that men and women show different patterns of delinquency to the extent they face unique adaptive problems. For instance, we might expect that females who find themselves in particularly hostile environments preferentially seek out male partners capable of enacting and defending against such aggression, as males tend to be more physically formidable (which is not to say that the women themselves might not be more physically aggressive as well). Any hypothetical shifts in mating preferences like these would not be captured by the present research particularly well, but it is nice to see the authors are at least thinking about what sex differences in patterns of delinquency might exist. It would be preferable if they were asking about those differences using this kind of a functional framework from the beginning, as that’s likely to yield more profitable insights and refine what questions get asked, but it’s good to see this kind of work all the same.

References: Abajobir, A., Kisely, S., Williams, G., Strathearnd, L., Clavarino, A., & Najman, J. (2016). Gender differences in delinquency at 21 years following childhood maltreatment: A birth cohort study. Personality & Individual Differences, 106, 95-103. 

Harris, J. (2009). The Nurture Assumption: Why Children Turn Out the Way They Do. Free Press.