He’s Climbing In Your Windows; He’s Snatching Your People Up

One topic that has been addressed by evolutionary psychologists that managed to draw a good deal of ire was rape. Given the sensitive nature of the issue, the criticisms that the theorizing about it brought were largely undeserved, reflecting, perhaps, a human tendency to mistake explanation with exculpation. Needless to say, at this point, sexual assault will be the topic for examination today, so if it’s the kind of thing that bothers you to read about, I suggest clicking away. Now that the warning has been made, if you’re still reading we can move forward. There has been some debate among evolutionary-minded researchers as to whether or not there are any rape-specific cognitive adaptations in humans, or whether rape represents a byproduct of other mating mechanisms. The debate remains unresolved for lack of unambiguous predictions or data. As the available data could be interpreted as consistent with both sides of the debate, the question remains a slippery and contentious one.

So do be careful if you decide to try and pick it up.

A paper by Felson & Cundiff (2012) suggests to have found some data they say support the byproduct view for rape. While I find myself currently favoring the byproduct explanation, I also find their interpretation of the evidence they bring to bear on the matter underwhelming. I actually find their interpretation of several matters off, but we’ll get to that later. First, let’s consider the research itself. The authors sought to examine existing data on robberies committed by lone males 12 years or older where a lone female was present at the time. From the robbery data, the authors were further interested in examining the subset of them that also involved a report of sexually assault. Towards this end, Felson & Cundiff (2012) reported data from approximately 45,000 robberies spanning from 2000-2007. Of those robberies, roughly 2% of them also involved a sexual assault, yielding about 900 cases for examination. As an initial note, the 2% figure would seem to suggest, to me, anyway, that in most instances of robbery/sexual assault, the assaults tended to not be preplanned; they look more opportunistic.

From this sample, the authors first examined what effect the female victim’s age had on the likelihood of a sexual assault being reported during the robbery. As it turns out, the age of the woman was a major determinant: women at the highest risk of being assaulted were in the 15-29 age range (with the peak being within the 20-24 year old age range), where the average risk of a sexual assault was around 2.5%. Before this age range, the risk of assault is substantially lower, around 1.3%. After 29 years, the rate begins to decline, dropping markedly after 40, down to around an average of 0.5%. In terms of opportunistic sexual assaults, then, male robbers appear to target women in their fertile years at disproportionate frequencies, presumably partially or largely on the basis of victim’s physical attractiveness. This finding appears consistent with previous work that had found the average age of a female who was the victim of a robbery alone was 35, while the average age of a robbery/assault victim was 27.9; about 7 years of difference. Any theories of rape that assume the act is motivated by power and not by sex would seem to have a very difficult time accounting for this pattern in the data.

Next, the authors turned their attention towards characteristics of the male robbers that predict whether or not an assault was reported. The results showed that the likelihood of a sexual assault increased as the males reached sexual maturity and steadily increased further until about their mid-thirties, after which they began to decline. Further, regardless of their age, the robbers didn’t show much in the way of variance in terms of the age of women they tended to target. That is to say whether the man was in his late teens or his late forties, they all seemed to preferentially target younger women nearer to their peak fecundity. The one exception to this pattern were the males aged 12-17, who seemed to even more disproportionately prefer women in their teens and early twenties. Felson & Cundiff (2012) note that this pattern of preferences is not typically observed in consensual relationships, where men and women tend to pair up around similar ages. This suggests that older men’s patterns of engaging in relationships with older women likely represents the relative aversion of younger women to the older males; not a genuine preference on the part of men for older women per se.

Though it’s difficult to imagine why older men aren’t preferred…

That’s not to say that older men may not have a preference for pursing relatively older women, just that such a preference wouldn’t be driven by the woman’s age. Such a preference might well be driven by other factors, however, such as the relative willingness of a woman to enter into a relationship with the man in question. There’s not much point for a man in pursuing women they’re unlikely to ever attain success with, even if those women are highly attractive; better to spend that time and energy in domains more liable to payoff. Louis C.K. sums the issue up neatly in one of his stand-up routines: “to me, you’re not a woman until you’ve had a couple of kids and your life is in the toilet…[if you're a younger girl] I don’t want to fuck you…[alright] I do want to fuck you, but you won’t fuck me, so fuck you”. When such tradeoffs can be circumvented – as is the case in sexual assault – a person’s underlying preferences for certain characteristics can be more readily assessed.

This brings us to my complaints with the paper. As I mentioned initially, there’s an ongoing debate as to whether or not men have cognitive mechanisms designed for rape specifically, or whether rape is generated as a byproduct of mechanisms designed for other purposes. Felson & Cundiff (2012) suggest that their data support the byproduct interpretation. Why? Because they found that women in the 15-29 age range who were sexually assaulted were less likely to be raped than older women. This pattern of data is supposed to support the byproduct hypothesis because, I think, the authors are positing some specific motivation for sex acts that could result in conception, rather than some more general interest in sexual behavior. It’s hard to say, since the authors fail to lay out the theory behind their hypothesis with precision. This strikes me as somewhat of a strange argument, though, as it would essentially posit that sexual acts that are unlikely to result in conception (such as oral or anal sex) are motivated by a different set of cognitive mechanisms that an interest in vaginal sex. While that might potentially be the case, I’ve never seen a case made for it, and there isn’t a strong one to be found in the paper.

The other complaint I have is that the authors use a phrase that’s a particular pet peeve of mine: “..our results are consistent with the predictions from evolutionary psychology”. This phrase always troubles me because evolutionary psychology, as field, does not make a set of uniform predictions about sexual behavior. Their results may well be consistent with some sub-theories derived by psychologists using an evolutionary framework – such as sexual strategies theory – but they are not derived from evolutionary psychology more broadly. To say that a result is consistent or inconsistent with evolutionary psychology is to imply that such a finding supports or fails to support the foundational assumptions of the field; assumptions which have to do with the nature of information processing mechanisms. While this might seem like a minor semantic point at first, I feel it’s actually a rather deep issue. It’s a frequent mistake that many of evolutionary psychology’s critics make when attempting to write off the entire field on the basis of a single idea they don’t like. To the extent that such inaccurate generalizations serve to hinder people’s engagement with the field, there’s a problem to be addressed.

And if you’re not willing to engage with me, I’d like the ring back.

As evolutionary psychology more broadly doesn’t deliver specific predictions about rape, neither the hypothesis that rape is an adaptation or a byproduct should rightly be considered the official evolutionary psychology perspective on the topic; this would be the case regardless of whether the evidence strongly supported one side or the other, I might add. While the the current research doesn’t speak to either of these possibilities distinctly, it does manage to speak against the idea that rape isn’t about sex, adding to the already substantial evidence that such a view is profoundly mistaken. Of course, the not-sex explanation was always more of a political slogan than a scientific one, so the lack of empirical support for it might not prove terribly troubling for its supporters.

References: Felson, R., & Cundiff, P. (2012). Age and sexual assault during robberies Evolution and Human Behavior, 33 (1), 10-16 DOI: 10.1016/j.evolhumbehav.2011.04.002

18 comments on “He’s Climbing In Your Windows; He’s Snatching Your People Up

  1. Marmaloid on said:

    Rape, simply a byproduct? For that to be true wouldn’t it mean that raping women didn’t significantly affect a prehistoric man’s reproductive success, so that it wouldn’t be selected for?

    • Jesse Marczyk on said:

      Sort of. The question is more precisely phrased as follows: were some of cognitive mechanisms that generate the output of rape selected for because of that effect, or were those mechanisms selected for because of other functions. Essentially, it’s asking whether there are any, for lack of a better term, rape-specific cognitive adaptations.

      • Marmaloid on said:

        Ok, but isn’t it a bit unlikely that, as long as you could get away with it, forcibly impregnating women wouldn’t have been advantageous in caveman times?

        • Jesse Marczyk on said:

          Sounds reasonable. The key phrase there, of course, “if you could get away with it”.

          • Marmaloid on said:

            Of course, you’d have to be wise about it. Don’t go raping the local hard man’s daughter, go for the unprotected women you come across when you’re traveling or the women in a tribe you’ve invaded and conquered.

          • Jesse Marczyk on said:

            The trick is to deliver predictions that uniquely support one view. So far, I haven’t seen good empirical tests along those lines.

        • Marmaloid on said:

          What do you mean?

          • Jesse Marczyk on said:

            What unique design features can one predict on the basis of the assumption that rape has some unique cognitive mechanism?

          • Marmaloid on said:

            I see what you’re getting at. Maybe there doesn’t need to be a specific module for rape. Instead raping could be one specific way under certain circumstances of achieving the more general goal of impregnating females.

            This doesn’t really mean that rape is just a byproduct and not an adaption, just that evolution has equipped men with more generalized sexual motivations that can result in rape under the appropriate conditions.

  2. Bussicks on said:

    “…with the peak being within the 20-24 year old age range…”

    Is the same peak seen in the age of women that men prefer for consensual sex?

    • Jesse Marczyk on said:

      Approximately, yes; I think it is, though the specifics vary as to the nature of the relationship (short vs. long term, for instance)

      • Bussicks on said:

        Do you know any studies or surveys about this you could link to? It’s something I’m interested in. Thanks.

        • Jesse Marczyk on said:

          You could start here (paper), and the book by the same authors is good as well.

          • Nuclear Wheelchair on said:

            I’ve just found this this paper on David Buss’s site. It mentions that a women’s RV peaks at about 17. Do you know how this was measured?

          • Jesse Marczyk on said:

            I believe it’s a theoretically-driven value, falling sometime after a woman is sexually mature but before she has had her first child, meaning she has the maximal number of reproductive years ahead of her. At least that’s what I just found looking over that section in his book.

          • Nuclear Wheelchair on said:

            I’ve found a book that explains it. I have a good read of it tonight.

          • Nuclear Wheelchair on said:

            What I’ve gathered is that the RV of a female is basically the number of future offspring she can be expected to contribute to the population and that this will peak at her first pregnancy.

            Suppose if a women lives all the way the end of her reproductive life she can be expected to leave behind on average a total number T offspring and that the age she starts reproducing is F. If the probability of a female under age F surviving to F is p then her expected amount of future offspring will be pT which is less than T. The lowest value of p will be for newborns and it will rise to 1 at age F so a women’s RV peaks at the start of her reproductive life.

            Peak reproductive value is just a fancy way of saying average age of first pregnancy, I think.

          • Jesse Marczyk on said:

            That sounds right. At least average age of first potential pregnancy, or slightly before.