Why Women Are More Depressed Than Men

Women are more likely to be depressed than men; about twice as likely here in the US, as I have been told. It’s an interesting finding, to be sure, and making sense of it poses a fun little mystery (as making sense of many things tends to). We don’t just want to know that women are more depressed than men; we also want to know why women are more depressed. So what are the causes of this difference? The Mayo Clinic floats a few explanations, noting that this sex difference appears to emerge around puberty. As such, many of the explanations they put forth center around the problems that women (but not men) might face when undergoing that transitional period in their life. These include things like increased pressure to achieve in school, conflict with parents, gender confusion, PMS, and pregnancy-related factors. They also include ever-popular suggestions such as societal biases that harm women. Now I suspect these are quite consistent with the answers you would get if queried your average Joe or Jane on the street as to why they think women are more depressed. People recognize that depression often appears to follow negative life events and stressors, and so they look for proximate conditions that they believe (accurately or not) disproportionately affect women.

Boys don’t have to figure out how to use tampons; therefore less depression

While that seems to be a reasonable strategy, it produces results that aren’t entirely satisfying. First, it seems unlikely that women face that much more stress and negative life events than men do (twice as much?) and, secondly, it doesn’t do much to help us understand individual variation. Lots of people face negative life events, but lots of them also don’t end up spiraling into depression. As I noted above, our understanding of the facts related to depression can be bolstered by answering the why questions. In this case, the focus many people have is on answering the proximate whys rather than the ultimate ones. Specifically, we want to know why people respond to these negative life events with depression in the first place; what adaptive function depression might have. Though depression reactions appear completely normal to most, perhaps owing to their regularity, we need to make that normality strange. If, for example, you imagine a new mouse mother facing the stresses of caring for her young in a hostile world, a postpartum depression on her part might seem counterproductive: faced with the challenges of surviving and caring for her offspring, what adaptive value would depressive symptoms have? How would low energy, a lack of interest in important everyday activities, and perhaps even suicidal ideation help make her situation better? If anything, they would seem to disincline her from taking care of these important tasks, leaving her and her dependent offspring worse off. This strangeness, of course, wouldn’t just exist in mice; it should be just as strange when we see it in humans.

The most compelling adaptive account of depression I’ve read (Hagen, 2003) suggests that the ultimate why of depression focuses on social bargaining. I’ve written about it before, but the gist of the idea is as follows: if I’m facing adversity that I am unlikely to be able to solve alone, one strategy for overcoming that problem is to recruit others in the world to help me. However, those other people aren’t always forthcoming with the investment I desire. If others aren’t responding to my needs adequately, it would behoove me to try and alter their behavior so as to encourage them to increase their investment in me. Depression, in this view, is adapted to do just that. The psychological mechanisms governing depression work to, essentially, place the depressed individual on a social strike. When workers are unable to effectively encourage an increased investment from their employers (perhaps in the form of pay or benefits), they will occasionally refuse to work at all until their conditions improve. While this is indeed costly for the workers, it is also costly for the employer, and it might be beneficial for the employer to cave to the demands rather than continue to face the costs of not having people work. Depression shows a number of parallels to this kind of behavior, where people withdraw from the social world – taking with them the benefits they provided to others – until other people increase their investment in the depressed individual to help see them through a tough period.

Going on strike (or, more generally, withdrawing from cooperative relationships), of course, is only one means of getting other people to increase their investment in you; another potential strategy is violence. If someone is enacting behaviors that show they don’t value me enough, I might respond with aggressive behaviors to get them to alter that valuation. Two classic examples of this could be shooting someone in self-defense or a loan-shark breaking a delinquent client’s legs. Indeed, this is precisely the type of function that Sell et al (2009) proposed that anger has: if others aren’t giving me my due, anger motivates me to take actions that could recalibrate their concern for my welfare. This leaves us with two strategies – depression and anger – that can both solve the same type of problem. The question arises, then, as to which strategy will be the most effective for a given individual and their particular circumstances. This raises a rather interesting possibility: it is possible that the sex difference in depression exists because the anger strategy is more effective for men, whereas the depression strategy is more effective for women (rather than, say, because women face more adversity than men). This would be consistent with the sex difference in depression arising around puberty as well, since this is when sex differences in strength also begin to emerge. In other words, both men and women have to solve similar social problems; they just go about it in different ways. 

“An answer that doesn’t depend on wide-spread sexism? How boring…”

Crucially, this explanation should also be able to account for within-sex differences as well: while men are more able to successfully enact physical aggression than women, not all men will be successful in that regard since not all men possess the necessary formidability. The male who is 5’5″ and 130 pounds soaking wet likely won’t win against his taller, heavier, and stronger counterparts in a fight. As such, men who are relatively weak might preferentially make use of the depression strategy, since picking fights they probably won’t win is a bad idea, while those who are on the stronger side might instead make use of anger more readily. Thankfully, a new paper by Hagen & Rosenstrom (2016) examines this very issue; at least part of it. The researchers sought to test whether upper-body strength would negatively predict depression scores, controlling for a number of other, related variables.

To do so, they accessed data from the National Health and Nutrition Examination Survey (NHANES), netting a little over 4,000 subjects ranging in age from 18-60. As a proxy for upper-body strength, the authors made use of the measures subjects had provided of their hand-grip strength. The participants had also filled out questions concerning their depression, height and weight, socioeconomic status, white blood cell count (to proxy health), and physical disabilities. The researchers predicted that: (1) depression should negatively correlate with grip-strength, controlling for age and sex, (2) that relationship should be stronger for men than women, and (3) that the relationship would persist after controlling for physical health. About 9% of the sample qualified as depressed and, as expected, women were more likely to report depression than men by about 1.7 times. Sex, on its own, was a good predictor of depression (in their regression, ß = 0.74).

When grip-strength was added into the statistical model, however, the effect of sex dropped into the non-significant range (ß = 0.03), while strength possessed good predictive value (ß = -1.04). In support of the first hypothesis, then, increased upper-body strength did indeed negatively correlate with depression scores, removing the effect of sex almost entirely. In fact, once grip strength was controlled for, men were actually slightly more likely to report depression than women (though this didn’t appear to be significant). Prediction 2 was not supported, however, with their being no significant interaction between sex and grip-strength on measures of depression. This effect persisted even when controlling for socioeconomic status, age, anthropomorphic, and hormonal variables. However, physical disability did attenuate the relationship between strength and depression quite a bit, which is understandable in light of the fact that physically-disabled individuals likely have their formidability compromised, even if they have stronger upper bodies (an example being a man in a wheelchair having good grip strength, but still not being much use in a fight). It is worth mentioning that the relationship between strength and depression appeared to grow larger over time; the authors suggest this might have something to do with older individuals having more opportunities to test their strength against others, which sounds plausible enough. 

Also worth noting is that when depression scores were replaced with suicidal ideation, the predicted sex-by-strength interaction did emerge, such that men with greater strength reported being less suicidal, while women with greater strength reported being more suicidal (the latter portion of which is curious and not predicted). Given that men succeed at committing suicide more often than women, this relationship is probably worth further examination.  

“Not today, crippling existential dread”

Taken together with findings from Sell et al (2009) – where men, but not women, who possessed greater strength reported being quicker to anger and more successful in physical conflicts – the emerging picture is one in which women tend to (not consciously) “use” depression as a means social bargaining because it tends to work better for them than anger, whereas the reverse holds true for men. To be clear, both anger and depression are triggered by adversity, but those events interact with an individual’s condition and their social environment in determining the precise response. As the authors note, the picture is likely to be a dynamic one; not one that’s as simple as “more strength = less depression” across the board. Of course, other factors that co-vary with physical strength and health – like attractiveness – could also being playing a roll in the relationship with depression, but since such matters aren’t spoken to directly by the data, the extent and nature of those other factors is speculative.

What I find very persuasive about this adaptive hypothesis, however – in addition to the reported data – is that many existing theories of depression would not make the predictions tested by Hagen & Rosenstrom (2016) in the first place. For example, those who claim something like, “depressed people perceive the world more accurately” would be at a bit of a loss to explain why those who perceive the world more accurately also seem to have lower upper-body strength (they might also want to explain why depressed people don’t perceive the world more accurately, either). A plausible adaptive hypothesis, on the other hand, is useful for guiding our search for, and understanding of, the proximate causes of depression.

References: Hagen, E.H. (2003). The bargaining model of depression. In: Genetic and Cultural Evolution of Cooperation, P. Hammerstein (ed.). MIT Press, 95-123

Hagen, E. & Rosenstrom, T. (2016). Explain the sex difference in depression with a unified bargaining model of anger and depression. Evolution, Medicine, & Public Health, 117-132

Sell, A., Tooby, J., & Cosmides, L. (2009). Formidability and the logic of human anger. Proceedings of the National Academy of Sciences, 106, 15073-78.

Does Grief Help Recalibrate Behavior?

Here’s a story which might sound familiar to all of you: one day, a young child is wandering around in the kitchen while his parents are cooking. This child, having never encountered a hot stove before, reaches up and brushes his hand against the hot metal. Naturally, the child experiences a physical pain and withdraws his hand. In order to recalibrate his behavior so as to not avoid future harms, then, the child spends the next week unable to get out of bed – owing to a persistent low-energy – and repeatedly thinks about touching the hot stove and how sad it made him feel. For the next year, the child returns to the spot where he burned his hand, leaving flowers on the spot, and cries for a time in remembrance. OK; so maybe that story doesn’t sound familiar at all. In fact, the story seems absurd on the face of it: why would the child go through all that grief in order to recalibrate their stove-touching behavior when they could, it seems, simply avoid touching the hot stove again? What good would all that additional costly grief and depression do? Excellent question.

Unfortunately, chain emails do not offer learning trials for recalibration.

In the case of the hot stove, we could conclude that grief would likely not add a whole lot to the child’s ability to recalibrate their behavior away from stove-touching. It doesn’t seem like a very efficient way of doing so, and the fit between the design features of grief and recalibration seem more than a bit mismatched. I bring these questions up in response to a suggestion I recently came across by Tooby & Cosmides, with whom I generally find myself in agreement with (it’s not a new suggestion; I just happened to come across it now). The pair, in discussing emotions, have this to say about grief:

Paradoxically, grief provoked by death may be a byproduct of mechanisms designed to take imagined situations as input: it may be intense so that, if triggered by imagination in advance, it is properly deterrent. Alternatively-or additionally-grief may be intense in order to recalibrate weightings in the decision rules that governed choices prior to the death. If your child died because you made an incorrect choice (and given the absence of a controlled study with alternative realities, a bad outcome always raises the probability that you made an incorrect choice), then experiencing grief will recalibrate you for subsequent choices. Death may involve guilt, grief, and depression because of the problem of recalibration of weights on courses of action. One may be haunted by guilt, meaning that courses of action retrospectively judged to be erroneous may be replayed in imagination over and over again, until the reweighting is accomplished.

So Tooby and Cosmides posit two possible functions for grief here: (1) there isn’t a function per se; it’s just a byproduct of a mechanism designed to use imagined stimuli to guide future behavior, and (2) grief might help recalibrate behavior so as to avoid outcomes that previously have carried negative fitness consequences. I want to focus on the second possibility because, as I initially hinted at, I’m having a difficult time seeing the logic in it.

One issue I seem to be having concerns the suggestion that people might cognitively replay traumatic or grief-inducing events over and over in order to better learn from them. Much like the explanation often on offer for depression, then, grief might function to help people make better decisions in the future. That seems to be the suggestion Tooby & Cosmides are getting at, anyway. As I’ve written before, I don’t think this explanation in plausible on the face of it. At least in terms of depression, there’s very little evidence that depression actually helps people make better decisions. Even if it did, however, it would raise the question as to why people ever don’t make use of this strategy. Presumably, if people could learn better by replaying events over and over, one might wonder why we ever don’t do that; why would we ever perform worse, when we could be performing better?  In order to avoid making what I nicknamed the Dire Straits fallacy ( from their lyric “money for nothing and the chicks for free“), the answer to that question would inevitably involve referencing some costs to replaying events over and over again. If there were no such costs to replay, and replay led to better outcomes, replay should be universal, which it isn’t; at least not to nearly the same degree. Accordingly, any explanation for understanding why people use grief as a mechanism for improved learning outcomes would need to make some reference as to why grief-struck individuals are more able to suffer those costs for the benefits continuous replay provides. Perhaps such an explanation exists, but it’s not present here.

One might also wonder what replaying some tragic event over and over would help one learn from it. That is, does the replaying the event actually help one extract additional useful information from the memory? As we can see from the initial example, rumination is often not required to quickly and efficiently learn connections between behaviors and outcomes. To use the Tooby & Cosmides example, if your child died because you made an incorrect choice, why would ruminating for weeks or longer help you avoid making that choice again? The answer to that question should also explain why rumination would not be required for effective learning in the case of touching the hot stove.

It should only be a few more weeks of this until she figures out that babies need food.

One might also suggest that once the useful behavioral-recalibration-related information has been extracted from the situation, replaying the grief-inducing event would seem to be wasted time, so the grief should stop. Tooby & Cosmides make this suggestion, writing:

After the 6-18 month period, the unbidden images suddenly stop, in a way that is sometimes described as “like a fever breaking”: this would be the point at which the calibration is either done or there is no more to be learned from the experience

The issue I see with that idea, however, is that unless one is positing it can take weeks, months, or even years to extract the useful information from the event, then it seems unlikely that much of that replay involves helping people learn and extract information. Importantly, to the extent that decisions like these (i.e. “what were you doing that led to your child’s death that you shouldn’t do again”) were historically recurrent and posed adaptive problems, we should expect evolved cognitive decision making modules to learn from them fast and efficiently. A mechanism that takes weeks, months, or even years to learn from an event by playing it over and over again should be at a massive disadvantage, relative to a mechanism that can make those same learning gains in seconds or minutes. A child that needed months to learn to not touch a hot stove might be at a risk of touching the stove again; if the child immediately learned to not do so, there’s little need to go over grieving about it for months following the initial encounter. Slow learning is, on the whole, a bad thing which carries fitness costs; not a benefit. Unless there’s something special about grief-related learning that requires it takes so long – some particularly computationally-demanding problem – then the length of grief seems like a peculiar design feature for recalibrating one’s own behavior.

This, of course, all presumes that the grief-recalibration learning mechanisms know how to recalibrate behavior in the first place. If your child died because of a decision you made, there are likely very many decisions that you made which might or might not have contributed to that outcome. Accordingly, there are very many ways in which you might potentially recalibrate your behavior to avoid such a future outcome again, very few of which will actually be of any use. So your grief mechanism should need to know which decisions to focus on at a minimum. Further still, the mechanism would need to know if recalibration was even possible in the first place. In the case of a spouse dying from something related to old age or a child dying from an illness or accident, all the grieving in the world wouldn’t necessarily be able to effect any useful change the next time around. So we might predict that people should only tend to grieve selectively: when doing so might help avoid such outcomes in the future. This means people shouldn’t tend to grieve when they’re older (since they have less time to potentially change anything) or about negative outcomes beyond their control (since no recalibration would help). As far as I know (which, admittedly, isn’t terribly far in this domain) this isn’t that case. Perhaps an astute reader could direct me to research where predictions like these have been tested.

Finally, humans are far from the only species which might need to recalibrate their behavior. Now it’s difficult to say precisely as to what other species feel, since you can’t just ask them, but do other species feel grief the same way humans do? The grief-as-recalibration model might predict that they should. Now, again, the depth of my knowledge on grief is minimal, so I’m forced to ask these questions out of genuine curiosity: do other species evidence grief-related behaviors? If so, in what contexts are these behaviors common, and why might those contexts be expected to require more behavioral recalibration than non-grief-inducing situations? If animals do not show any evidence of grief-related behaviors, why not? These are all matters which would need to be sorted out. To avoid the risk of being critical without offering any alternative insight, I would propose an alternative function for grief similar to what Ed Hagen proposed for depression: grief functions to credibly signal one’s social need.

“Aww. Looks like someone needs a hug”

Events that induce grief – like the loss of close social others or other major fitness costs – might tend to leave the griever in a weakened social position. The loss of mates, allies, or access to resources poses major problems to species like us. In order to entice investment from others to help remedy these problems, however, you need to convince those others that you actually do have a legitimate need. If your need is not legitimate, then investment in your might be less liable to payoff. The costly extended periods of grief, then, might help signal to others that one’s need is legitimate, and make one appear to be a better target of subsequent investment. The adaptive value of grief in this account lies not in what it makes the griever do per se; what the griever is doing is likely maladaptive in and of itself. However, that personally-maladaptive behavior can have an effect on others, leading them to provide benefits to the grieving individuals in an adaptive fashion. In other words, grief doesn’t serve to recalibrate the griever’s behavior so much as it serves to recalibrate the behavior of social others who might invest in you.

An Implausible Function For Depression

Recently, I was involved in a discussion about experimenter-induced expectation biases in performance, also known as demand characteristics. The basic premise of the idea runs along the following lines: some subjects in your experiment are interested in pleasing the experimenter or, more generally, trying to do “well” on the task (others might be trying to undermine your task – the “screw you” effect – but we’ll ignore them for now). Accordingly, if the researchers conducting an experiment are too explicit about the task, or drop hints as to what the purpose is or what results they are expecting, even hints that might seem subtle, they might actually create the effect they are looking for, rather than just observe it. However, the interesting portion of the discussion I was having is that some people seemed to think you could get something for nothing from demand characteristics. That is to say some people seem to think that, for instance, if the experimenter thinks a subject will do well on a math problem, that subject will actually get better at doing math.

Hypothesis 1: Subjects will now be significantly more bullet-proof than they previously were.

This raises the obvious question: if certain demand characteristics can influence subjects to perform better or worse at some tasks, how would such an effect be achieved? (I might add that it’s a valuable first step to ensure that the effect exists in the first place which, in the case of stereotype threat with regard to math abilities, it might well not) It’s not as if these expectations are teaching subjects any new skills, so whatever information is being made use of (or not being made use of, in some cases) by the subject must have already been potentially accessible. No matter how much they might try, I highly doubt that researchers are able to simply expect subjects into suddenly knowing calculus or lifting twice as much weight as they normally can. The question of interest, then, would seem to become: given that subjects could perform better at some important task, why would they ever perform worse at it? Whatever specific answer one gives for that question, it will inevitably include the mention of trade-offs, where being better at some task (say, lifting weights) carries costs in other domains (such as risks of injury or the expenditure of energy that could be used for other tasks). Subjects might perform better on math problems after exercise, for instance, not because the exercise makes them better at math, but because there are fewer cognitive systems currently distracting the math one.

This brings us to depression. In attempting to explain why so many people get depressed, there are plenty of people who have suggested that there is a specific function to depression: people who are depressed are thought to be more accurate in some of their perceptions, relative to those who are not depressed. Perhaps, as Neel Burton and, curiously, Steven Pinker suggest, depressed individuals might do better at assessing the value of social relationships with others, or at figuring out when to stop persisting at a task that’s unlikely to yield benefits.  The official title for this hypothesis is depressive realism. I do appreciate such thinking insomuch as researchers appear to be trying to explain some psychological phenomenon functionally. Depressed people are more accurate in certain judgments, being more accurate in said judgments leads to some better social outcomes, so there are some adaptive benefits to being depressed. Neat. Unfortunately, such a line of thinking misses the aforementioned critical mention of trade-offs: specifically, if depressed people are supposed to perform better at such tasks, if people have the ability to better assess social relationships and their control over them, why would people ever be worse at those tasks?

If people hold unrealistically positive cognitive biases about their performance, and these biases cause people to, on the whole, do worse than they would without them, then the widespread existence of those positive biases need to be explained. The biases can’t simply exist because they make us feel good. Not only would such an explanation be uninformative (in that it doesn’t explain why we’d feel bad without them), but it would also be useless, as “feeling good” doesn’t do anything evolutionary useful. Notwithstanding those issues, however, the depressive realism hypothesis doesn’t even seem to be able to explain the nature of depression very well; not on the face of it anyway. Why should increasing one’s perceptual accuracy in certain domains go hand-in-hand with low energy levels or loss of appetite? Why should women be more likely to be depressed than men? Why should increases in perceptual accuracy similarly increase an individual’s risk of suicidal behavior? None of those symptoms seem like the hallmark of good, adaptive design when considered in the context of overcoming other, unexplained, and apparently maladaptive positive biases.

“We’ve manged to fix that noise the car made when it started by making it unable to start”

So, while the depressive realism hypothesis manages to think about functions, it would appear to fail to consider other relevant matters. As a result, it ends up positing a seemingly-implausible function for depression; it tries to get something (better accuracy) for nothing, all without explaining why other people don’t get that something as well. This might mean that depressive realism identifies an outcome of being depressed instead of explaining depression, but even that much is questionable. This returns to the initial point I made, in that one wants to be sure that the effect in question even exists in the first place. A meta-analysis of 75 studies of depressive realism conducted by Moore & Fresco (2012) did not yield a great deal of support for the effect being all that significant or theoretically interesting. While they found evidence of some depressive realism, the effect size of that realism was typically around or less than a tenth of a standard deviation in favor of the depressed individuals; an effect size that the authors repeatedly mentioned was “below [the] convention for a small effect” in psychology. In many cases, the effect sizes were so close to zero that they might of as well have been zero for all practical purposes; in other cases it was the non-depressed individuals who performed better. It would seem that depressed people aren’t terribly more realistic; certainly not relative to the costs that being depressed brings. More worryingly for the depressive realism hypothesis, the effect size appeared to be substantially larger in studies using poor methods of assessing depression, relative to studies using better methods. Yikes.

So, just to summarize, what we’re left with is an effect that might not exist and a hypothesis purporting to explain that possible effect which makes little conceptual sense. To continue to pile on, since we’re already here, the depressive realism hypothesis seems to generate few, if any, additional testable predictions. Though there might well be plenty of novel predictions that flow from the suggestion that depressed people are more realistic than non-depressed individuals, there aren’t any that immediately come to my mind. Now I know this might all seem pretty bad, but let’s not forget that we’re still in the field of psychology, making this outcome sort of par for the course in many respects, unfortunate as that might seem.

The curious part of the depressive realism hypothesis, to me, anyway, is why it appears to have generated as much interest as it did. The meta-analysis found over 120 research papers on the topic, which is (a) probably not exhaustive and (b) not representative of any failures to publish research on the topic, so there has clearly been a great deal of research done on the idea. Perhaps it has something to do with the idea that there’s a bright side to depression; some distinct benefit that ought to make people more sympathetic towards those suffering from depression. I have no data that speaks to that idea one way or the other though, so I remain confused as to why the realism hypothesis has drawn so much attention. It wouldn’t be the first piece of pop psychology to confuse me in such a manner.

And if it confuses you too, feel free to stop by this site for more updates.

As a final note, I’m sure there are some people out there who might be thinking that though the depressive realism idea is, admittedly, lacking in many regards, it’s currently the best explanation for depression on offer. While such conceptual flaws are, in my mind, reason enough to discard the idea even in the event there isn’t an alternative on offer, there is, in fact, a much better alternative theory. It’s called the bargaining model of depression, and the paper is available for free here. Despite not being an expert on depression myself, the bargaining model seems to make substantially more conceptual sense while simultaneously being able to account for the existing facts about depression. Arguably, it doesn’t paint the strategy of depression in the most flattering light, but it’s at least more realistic.

References: Moore, M., & Fresco, D. (2012). Depressive realism: A meta-analytic review Clinical Psychology Review, 32 (6), 496-509 DOI: 10.1016/j.cpr.2012.05.004

Mothers And Others (With Benefits)

Understanding the existence and persistence of homosexuality in the face of its apparently reproductive fitness costs has left many evolutionary researchers scratching their heads. Though research into homosexuality has not been left wanting for hypotheses, every known hypothesis to date but one has had several major problems when it comes to accounting for the available data (and making conceptual sense). Some of them lack a developmental story; some fail to account for the twin studies; others posit benefits that just don’t seem to be there. What most of the aforementioned research shares in common, however, is its focus: male homosexuality. Female homosexuality has inspired considerably less hypothesizing, perhaps owing to the assumption, valid or not, that female sexual preferences played less of a role in determining fitness outcomes, relative to men’s. More precisely, physical arousal is required for men in order for their to engage in intercourse, whereas it is not necessarily required for women.

Not that lack of female arousal has ever been an issue for this fine specimen.

A new paper out in Evolutionary Psychology by Kuhle & Radtke (2013) takes a functional stab at attempting to explain some female homosexual behavior. Not the homosexual orientations, mind you; just some of the same-sex behavior. On this point, I would like to note that homosexual behavior isn’t what poses an evolutionary mystery anymore than other, likely nonadaptive behaviors, such as masturbation. The mystery is why an individual would be actively averse to intercourse with members of the opposite sex; their only path to reproduction. Nevertheless, the suggestion that Kuhle & Radtke (2013) put forth is that some female homosexual sexual behavior evolved in order to recruit female alloparent support. An alloparent is an individual who provided support for an infant but is not one of that infant’s parents. A grandmother helping to raise a grandchild, then, would represent a case of alloparenting. On the subject of grandmothers, some have suggested that the reason human females reach menopause so early in their lifespan – relative to other species who go on with the potential to reproduce until right around the point they die – is that grandmother alloparenting, specifically maternal grandmother, was a more valuable resource at the point, relative to direct reproduction. On the whole, alloparenting seems pretty important, so getting a hold of good resources for the task would be adaptive.

The suggestion that women might use same-sex sexual behavior to recruit female alloparental support is good, conceptually, on at least three fronts: first, it pays some mind to what is at least a potential function for a behavior. Most psychological research fails to think about function at all, much less plausible functions, and is all the worse because of it. The second positive part of this hypothesis is that it has some developmental story to go with it, making predictions about what specific events are likely to trigger the proposed adaptation and, to some extent, anyway, why they might. Finally, it is consistent with – or at least not outright falsified by – the existing data, which is more than you can say for almost all the current theories purporting to explain male homosexuality. On these conceptual grounds, I would praise the lesbian-sex-for-alloparenting model. On other grounds, both conceptual and empirical, however, I have very serious reservations.

The first of these reservations comes in form of the source of alloparental investment. While, admittedly, I have no hard data to bear on this point (as my search for information didn’t turn up any results), I would wager it’s a good guess that a substantial share of the world’s alloparental resources come from the mother’s kin: grandparents, cousins, aunts, uncles, siblings, or even other older children. As mentioned previously, some have hypothesized that grandmothers stop reproducing, at least in part, for that end. When alloparenting is coming from the female’s relatives, it’s unlikely that much, if any, sexual behavior, same-sex or otherwise, is involved or required. Genetic relatedness is likely providing a good deal of the motivation for the altruism in these cases, so sex would be fairly unnecessary. That thought brings me neatly to my next point, and it’s one raised briefly by the authors themselves: why would the lesbian sex even be necessary in the first place?

“I’ll help mother your child so hard…”

It’s unclear to me what the same-sex behavior adds to the alloparenting equation here. This concern comes in a number of forms. The first is that it seems adaptations designed for reciprocal altruism would work here just fine: you watch my kids and I’ll watch yours. There are plenty of such relationships between same-sex individuals, regardless of whether they involve childcare or not, and those relationships seem to get on just fine without sex being involved. Sure, sexual encounters might deepen that commitment in some cases, but that’s a fact that needs explaining; not the explanation itself. How we explain it will likely have a bearing on further theoretical analysis. Sex between men and women might deepen that commitment on account of it possibly resulting in conception and all the shared responsibilities that brings. Homosexual intercourse, however, does not carry that conception risk. This means that any deepening of the social connections homosexual intercourse might bring would most likely be a byproduct of the heterosexual counterpart. In much the same way, masturbation probably feels good because the stimulation sexual intercourse provides can be successfully mimicked by one’s hand (or whatever other device the more creative among us make use of). Alternatively, it could be possible that the deepening of an emotional bond between two women as the result of a sexual encounter was directly selected for because of it’s role in recruiting alloparent support, but I don’t find the notion particularly likely.

A quick example should make it clear why: for a woman who currently does not have dependent children, the same-sex encounters don’t seem to offer her any real benefit. Despite this, there are many women who continue to engage in frequent to semi-frequent same-sex sexual behaviors and form deep relationships with other women (who are themselves frequently childless as well). If the deepening of the bond between two women was directly selected for in the case of homosexual sexual behavior due to the benefits that alloparents can bring, such facts would seem to be indicative of very poor design. That is to say we should predict that women without children would be relatively uninterested in homosexual intercourse, and the experience would not deepen their social commitment to their partner. So sure, homosexual intercourse might deepen emotional bonds between the people engaging in it, which might in turn effect how the pair behave towards one another in a number of ways. That effect, however, is likely a byproduct of mechanisms designed for heterosexual intercourse; not something that was directly selected for itself. Kuhle & Radtke (2013) do say that they’re only attempting to explain some homosexual behavior, so perhaps they might grant that some increases in emotional closeness are the byproduct of mechanisms designed for heterosexual intercourse while other increases in closeness are due to selection for alloparental concerns. While possible, such a line of reasoning can set up a scenario where the hits for the theory can be counted as supportive and the misses (such as childless women engaging in same-sex sexual behaviors) dismissed as being the product of some other factor.

On top of that concern, the entire analysis rests on the assumption that women who have engaged in sexual behavior with the mother in question ought to be more likely to provide substantially better alloparental care than women who did not. This seems to be an absolutely vital prediction of the model. Curiously, that prediction is not represented in any of the 14 predictions listed in the paper. The paper also offers no empirical data bearing on this point, so whether homosexual behavior actually causes an increase in alloparental investment is in doubt. Even if we assume this point was confirmed however, it raises another pressing question: if same-sex intercourse raises the probability or quality of alloparental investment, why would we expect, as the authors predict, that women should only adopt this homosexual behavior as a secondary strategy? More precisely, I don’t see any particularly large fitness costs to women when it comes to engaging in same-sex sexual behavior but, under this model, there would be substantial benefits. If the costs to same-sex behavior are low and the benefits high, we should see it all the time, not just when a woman is having trouble finding male investment.

“It’s been real, but men are here now so…we can still be friends?”

On the topic of male investment, the model would also seem to predict that women should be relatively inclined to abandon their female partners for male ones (as, in this theory, women’s sexual interest in other women is triggered by lack of male interest). This is anecdotal, of course, but a fairly-frequent complaint I’ve heard from lesbians or bisexual women currently involved in a relationship with a woman is that men won’t leave them alone. They don’t seem to be wanting for male romantic attention. Now maybe these women are, more or less, universally assessing these men as being unlikely or unable to invest on some level, but I have my doubts as to whether this is the case.

Finally, given these sizable hypothesized benefits and negligible costs, we ought to expect to see women competing with other women frequently in the realm of attracting same-sex sexual interest. Same-sex sexual behavior should be expected to not only be cross-cultural universals, but fairly common as well, in much the same way that same-sex friendship is (as they’re hypothesized to serve much the same function, really). Why same-sex sexual interest would be relatively confined to a minority of the population is entirely unclear to me in terms of what is outlined in the paper. This model also doesn’t deal why any women, let alone the vast majority of them, would appear to feel averse to homosexual intercourse. Such aversions would only cause a woman to lose out the hypothesized alloparental benefits which, if the model is true, ought to have been substantial. Women who were not averse would have had more consistent alloparental support historically, leading to whatever genes made such attractions more likely to spread at the expense of women who eschewed it. Again, such aversions would appear to be evidence of remarkably poor design; if the lesbian-alloparents-with-benefits idea is true, that is…

References: Kuhle BX, & Radtke S (2013). Born both ways: The alloparenting hypothesis for sexual fluidity in women. Evolutionary psychology : an international journal of evolutionary approaches to psychology and behavior, 11 (2), 304-23 PMID: 23563096

Depressed To Impress

Reflecting on this morning’s usual breakfast cake brought to mind a thought that only people like myself think: the sugar in my breakfast is not sweet. Sweetness, while not a property of the sugar, is an experience generated by our mind when sugar is present on the tongue. We generally find the presence of sugar to be a pleasant experience, and often times find ourselves seeking out similar experiences in the future. The likely function of this experience is to motivate people to preferentially seek out and consume certain types of foods, typically the high-calorie variety. As dense packages of calories can be very beneficial to an organism’s survival, especially when they’re rare, the tendency to experience a pleasant sweetness in the presence of sugar was selected for; individuals who were indifferent between eating sand or honey were no one’s ancestors.

On a related note, there’s nothing intrinsically painful about damage done to your body. Pain, like sweetness, is an important signal; pain signals when your body is being damaged, in turn motivating people to stop doing or get away from whatever is causing the harm and avoiding making current injuries worse. Pain feels so unpleasant because, if it didn’t, the proper motivation would not be provided. However, in order to feel pain, an organism must have evolved that ability; it’s not present as a default, as evidenced by the rare people born without the ability to feel pain. As one could imagine, those who were indifferent to the idea of having their leg broken rarely ended up reproducing as well as others who found the experience excruciating.

Walk it off.

Sensations like pain or sweetness can be explained neatly and satisfyingly through these functional accounts. With these accounts we can understand why things that feel pleasant – like gorging myself on breakfast cake – are not always a good thing (when calories are abundant), whereas unpleasant feelings – like sticking your arm in a wood-chipper – can be vital to our survival. Conversely, lacking these functional accounts can lead to poor outcomes. For instance, treating a fever as a symptom of an infection to be reduced, rather than a body’s adaptive response to help fight the infection, can actually lead to a prolonging and worsening of said infection (Nesse & Williams, 1994). Before trying to treat something as a problem and make it go away just because it feels unpleasant, or not treat a problem because it might be enjoyable, it’s important to know what function those feelings might serve and what costs and benefits of reducing or indulging in them might entail. This brings us to the omnipresent subject of unpleasant feelings that people want to make go away in psychology: depression.

Depression, I’m told, is rather unpleasant to deal with. Most commonly triggered by a major, negative life event, depression leads to a loss of interest and engagement in almost all activities, low energy levels, and, occasionally, even suicide. Despite these apparent costs, depression continues to be a fairly prevalent complaint the world over, and is far more common among women than men. Given its predictability and prevalence, might there be a function behind this behavior? Any functional account of depression would need to both encompass these known facts, as well as purpose subsequent gains that would tend to outweigh these negative consequences. As reviewed by Hagen (2003), previous models of depression suggested that sadness served as a type of psychic pain: when one is unsuccessful in navigating the social world in some way, it is better to disengage from a failing strategy than to continue to pursue it, as one would be wasting time and energy that could be spent elsewhere. However, such a hypothesis fails to account for major depression, positing instead that major depression is simply a maladaptive byproduct of an otherwise useful system. Certainly, activities like eating shouldn’t be forgone because an unrelated social strategy has failed, nor should one engage in otherwise harmful behaviors (potentially suicidal ones) for similar reasons; it’s unclear from the psychic pain models why these particular maladaptive byproducts would arise and persist in the first place. For example, touching a hot pan causes one to rapid withdraw their hand, but it does not cause people to stop cooking food altogether for weeks on end.

Hagen (2003) puts forth the idea that depression functions primarily as a social bargaining mechanism. Given this function, Hagen suggests the following contexts should tend to provoke depressive episodes: a person should experience a perceived negative life event, the remedy to this event should be difficult or impossible to achieve on their own, and there must be conflict over other people’s willingness to provide assistance in achieving a remedy. Conflict is ubiquitous in the social realm of life; that much is uncontested. When confronted with a major negative life event, such as the death of a spouse or the birth of an unwanted child, social support from others can be its most important. Unfortunately for those in need, others people are not always the most selfless when it comes to providing for those needs, so the needy require methods of eliciting that support. While violence is one way to make others do what you’d like, it is not always the most reliable or safest method, especially if the source you’re attempting to persuade is stronger than you or outnumber you. Another route to compelling a more powerful other to invest in you is to increase the costs of not investing, and this can be done by simply withholding benefits that you can provide others until things change. Essentially, depression serves as a type of social strike, the goal of which is to credibly signal that one is not sufficiently benefiting from their current state, and is willing to stop providing benefits to others until the terms of their social contract have been renegotiated.

“What do we want? A more satisfying life. When do we want it? I’ll just be in bed until that time…whatever”

Counter-intuitive as it may sound, despite depression feeling harmful to the person suffering from it, the function of depression would be to inflict costs on others who have an interest in you being productive and helpful. By inflicting costs on yourself (or, rather, failing to provide benefits to others), you are thereby motivating others to help you to so they can, in turn, help themselves by regaining access to whatever benefits you can provide. Then again, perhaps this isn’t as counter-intuitive as it may sound, taking the case of suicide as an example. Suicide definitely represents a cost to other people in one’s life, from family members, to spouses, to children, to friends, or trade partners. It’s much more profitable to have a live friend or spouse capable of providing benefits to you than a dead one. Prior to any attempt being made, suicidal people tend to warn others of their intentions and, if any attempt is made, they are frequently enacted in manners which are unreliably lethal. Further still, many people, whether family or clinicians, view suicidal thoughts and attempts as cries for help, rather than as a desire to die per se, suggesting people have some underlying intuitions about the ultimate intentions of such acts. That a suicide is occasionally completed likely represents a maladaptive outcome of an evolutionary arms race between the credibility of the signal and the skepticism that others view the signal with. Is the talk about suicide just that – cheap talk – or is it actually a serious threat?

There are two social issues that depression needs to deal with that can also be accounted for in this model. The first issue concerns how depressed individuals avoid being punished by others. If an individual is taking benefits from other group members, but not reciprocating those benefits (whether due to depression or selfishness), they are likely to activate the cheater-detection module of the mind. As we all know, people don’t take kindly to cheaters and do not tend to offer them more support to help out. Rather, cheaters tend to be punished, having further costs inflicted upon them. If the goal of depression is to gain social support, punishment is the last thing that would help achieve that goal. In order to avoid coming off as a cheater, a depressed individual may need to forgo accepting many benefits that others provide, which would help explain why depressed individuals often give up activities like eating or even getting out of bed. A more-or-less complete shutdown of behavior might be required in order to avoid coming off as a manipulative cheater.

The second issue concerns the benefits that a depressed individual can provide. Let’s use the example of a worker going on strike: if this worker is particularly productive, having him not show up to work will be a genuine cost on the employer. However, if this worker either poorly skilled – thus able to deliver little, if any, benefits to the employer – or easily replaceable, not showing up to work won’t cause the employer any loss of sleep or money. Accordingly, in order for depression to be effective, the depressed individual needs to be socially valuable, and the more valuable they are seen as being, the more of a monopoly they hold over the benefits they provide, the more effective depression can be in achieving its goal. What this suggests is that depression would work better in certain contexts, perhaps when population sizes are smaller and groups more mutually dependent on one another – which would have been the social contexts under which depression evolved. What this might also suggest is that depression may become more prevalent and last longer the more replaceable people become socially due to certain novel features of our social environment; there’s little need to give a striking worker a raise if there are ten other capable people already lined up for his position.

You should have seen the quality of resumes I was getting last time I was single.

That depression is more common among women would suggest, then, that depression is a more profitable strategy for women, relative to men. There are several reasons this might be the case. First, women might be unable to engage in direct physical aggression as effectively as men, restricting their ability to use aggressive strategies to gain the support of others. Another good possibility is that, reproductively, women tend to be a more valuable resource (or rather, a limiting one) relative to men. Whereas almost all women had a valuable resource they could potentially restrict access to, not all men do. If men are more easily replaceable, they hold less bargaining power by threatening to strike. Another way of looking at the matter is that the costs men incur by being depressed and shutting down are substantially greater than the costs women do, or the costs they are capable of imposing on others aren’t as great. A depressed man may quickly fall in the status hierarchy, which would ultimately do more harm than the depressive benefits would be able to compensate for. It should also be noted that one of the main ways depression is alleviated is following a positive life change, like entering into a new relationship or getting a new job, which is precisely what the bargaining model would predict, lending further support to this model.

So given this likely function of depression, is it a mental illness that requires treatment? I would say no to the first part and maybe to the second. While generally being an unpleasant experience, depression, in this model, is no more of a mental illness than the experience of physical pain is. Whether or not it should be treated is, of course, up to the person suffering from it. There are very real costs to all parties involved when depression is active, and it’s certainly understandable why people would want to make them go away. What this model suggests is that, like treating a fever, just making the symptoms of depression go away may have unintended social costs elsewhere, either in the short- or long-term. While keeping employees from striking certainly keeps them working, it also removes some of their ability to bargain for better pay or working conditions. Similarly, simply relieving depression may keep people happier and more productive, but it may also lead them to accept less fulfilling or supportive circumstances in their life.

References: Hagen, E.H. (2003). The bargaining model of depression. In: Genetic and Cultural Evolution of Cooperation, P. Hammerstein (ed.). MIT Press, 95-123

Nesse, R.M., & Williams G.C. (1994). Why We Get Sick: The New Science Of Darwinian Medicine. Vintage books.