Evolutionary Psychology

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Robert Kurzban

The Evolutionary Psychology Blog

By Robert Kurzban

Robert Kurzban is an Associate Professor at the University of Pennsylvania and author of Why Everyone (Else) Is A Hypocrite. Follow him on Twitter: @rkurzban

Who’s Afraid of the Big, Bad Theory of Evolution?

Published 26 November, 2010

I think that Brian Scholl is one of the best experimental psychologists working in the field today. There, I said it.

I’ve known Brian – I’ll refer to him by first name here, and with apologies for the informality – for a number of years now, and he is not only among the best experimental psychologists working in the field today – there, I said it again – and he’s also a Really Nice Guy.

Ok, with that in mind, in today’s post, I’m going to briefly discuss, and then make some small, vaguely critical remarks about, a piece that recently came out of his lab, just published in Psychological Science. (Tao Gao was the first author on the paper.)

Brian does research on vision, and he and his collaborators have demonstrated a number of very interesting visual effects. This work investigates how people perceive, basically, pack hunting. They had subjects watch a display with shapes moving around and, in some of them, the shapes move randomly but “point toward” a disc that is also moving around. In one study, the subject controls a little green disc, and the task is to avoid the “wolf,” one of the other shapes on the screen. When there was a wolf pack in the stimulus – those shapes moving around, pointing at the subject’s sheep – performance wasn’t as good as when there wasn’t a wolf pack. In other words, the presence of the wolf pack stimuli, though irrelevant to the evasion task, impaired performance. (You have to check out the demos; I think this one is among the most compelling.)

The authors present a number of similar findings in a series of experiments, with a number of interesting control conditions. When there are good cues that multiple individuals are oriented toward a target, it really does give rise to a compelling sense of animacy.

Ok, now my quibble. Readers of this blog would probably have some ideas about why the “wolfpack effect” exists. It’s not crazy to think that humans – even humans living in New Haven, with little experience of being encircled by canid predators – have reliably developing mechanisms that are designed to deliver inferences and predictions about the social behavior of multiple individuals whose orientations toward a target are coordinated in a way that would facilitate predation.

It’s actually really hard to imagine that this research group didn’t have a function along these lines in mind when they designed the stimuli; and, of course, they call it the “wolfpack effect” because they do have such a function in mind. My question is, why is there no explicit reference to the evolved function of this system? The work is presented as a demonstration of an effect, but no explanation for its existence is offered for it other than, again, the references to wolfpacks. It’s a little like the authors are winking at the reader, saying, “look, we all know that we have an evolutionary explanation in mind – talking about wolfpacks makes this pretty clear – but we also all know that it’s unfashionable to say so. Therefore, we’ll just leave the animating idea, as it were, implicit.”

What is with the reluctance? Would the hypothesis that the human visual system is sensitive to these cues of coordinated activity become less falsifiable if a motivation for it in terms of evolved function were provided? What is the harm in being up front about the explanation for why these particular psychophysical cues draw the viewers’ attention in this way? In this context, I might note that Brian isn’t allergic to such functional explanations, in general. His work on motion-induced blindness (with Josh New) includes an idea about a particular function. (I’ll omit the details here; it’s a very cool idea though.)  But it’s clear that you wouldn’t have checked to see if this very particular pattern of stimuli – coordinated pointing toward a target – without the idea that this very particular pattern was useful for people to detect.

It seems to me that this is a symptom of a broader phenomenon. It’s fine to talk about evolved function for low level stuff, like the motion sensing and object recognition systems. (There, indeed, systems are named in terms of their function.) When the content is social, it becomes taboo to refer to evolved function.

I suppose Brian would say – feel free to chime in, my friend – that calling it the wolfpack effect is more or less naming an evolved function. Maybe. But if so, then there would have been little harm in saying that in the piece. Right?

  • Sarah

    I find it so interesting that you chose to comment on this. I had this same conversation with a good friend, although I was on the other side of the argument. Detailing the computational structure of the mechanism is everything that’s great about evoking an evolutionary theory without all of the baggage that comes from those loaded and abused words, “evolutionary psychology.” I’m sympathetic and torn as well, though, because 1) if more outstandingly brilliant people like Brian championed and took ownership of those words then perhaps it would drown out all of the misuse of the masses (though, when does that ever happen?) and 2) EP is held to such unfair standards of evidence that it would be nice to just have more of it (kind of like a “contact hypothesis” for theoretical orientation).

    But in the end I have to say that I am happy explicating computational mechanisms without evoking those words. They turn people off, they conjure semantic networks of misinformation and bad logic, and they rile people up in the wrong ways. I’m all about subversion. But I’m open to the idea that I’m one of those that Steve Pinker referred to when when he said “Behavioral Science is not for the faint-hearted.”

    • Nick

      Sarah, you’re probably right. By omitting any explicit mention of an ‘evolved’ or ‘adaptive’ function, they have saved themselves a headache. However, I think this is harmful to psychological research as a whole. Like Rob said, when quality research like this just gives a wink and a nudge to the evolutionary side of things, it not only prevents some people from potentially being turned on to EP, it also reinforces the idea that something needs to be obfuscated.

      Of course, it’s easy to complain and much harder to solve things, and I’m not sure if I have any good solutions.

  • Sarah

    I found a passage from Michael Gazzaniga in his book “The Mind’s Past” that I think makes a compelling argument for the focus of evolved functions in psychological research:

    All kinds of things immediately get in our way when we try to think about what the brain does. The human brain, with zillions of capacities and devices for helping us make better decisions about how to enhance our reproductive success, can do many other things along the way. While a computer can be used to compute, which is why it was built, it also makes one hell of a paperweight. The finely-tuned human brain can engage primal issues of sexual selection , or it can develop the second law of thermodynamics. Understanding how it does the latter may not inform us of what it normally does and how it does it.

    Most scientists, though , concentrate on the incidental mechanisms, which is a pity. If the evolutionary perspective is simply set aside, the data collected by psychologists and neuroscientists are likely to be grossly misinterpreted. The far-reaching implication of the evolutionary view is that models built to ex plain psychological and behavioral processes exam.ine only the “noise” of the honed neural system devoted to making decisions about survival…

    I think that many psychological evaluations are superficial. They explain only the noise, or unattended by-products, of a biological system rather than how the system works and what it is capable of doing. They are indeed spandrels.

    Obviously the Gao et al. paper is not guilty of this, but much research would benefit from this distinction and focus.

    • http://thoughtsfromthestreet.com H. J. Smith

      Very interesting quote Sarah; thanks. Even within the limited context of this quote, as posted, it makes a lot of sense; it presents a hypothesis worthy of serious consideration. I think I’m going to read Michael Gazzaniga’s book.

      • Sarah

        H.J., I highly recommend it. Here is another wonderful section from the prologue:

        Over a hundred years ago William James lamented, “I wished by treating Psychology like a natural science, to help her to become one.” Well, it never occurred. Psychology, which for many was the study of mental life, gave way during the past century to other disciplines. Today the mind sciences are the province of evolutionary biologists, cognitive scientists, neuroscientists, psychophysicists, linguists, computer scientists—you name it. This book is about special truths that these new practitioners of the study of mind have unearthed.

        Psychology itself is dead. The odd thing is that everyone but its practitioners knows about the death of psychology. The grand questions originally asked by those trained in classical psychology have evolved into matters other scientists can address. My dear friend the late Stanley Schachter of Columbia University told me just before his death that his beloved field of social psychology was not, after all, a cumulative science. Yes, scientists keep asking questions and using the scientific method to answer them, but the answers don’t point to a body of knowledge where one result leads to another. It was a strong statement—one that he would be the first to qualify. But he was on to something. The field of psychology is not the field of molecular biology, where new discoveries building on old ones are made every day.

        This is not to say that psychological processes and psychological states are uninteresting, even boring, subjects. On the contrary, they are fascinating pieces of the mysterious unknown that many curious minds struggle to understand. How the brain enables mind is the question to be answered in the twenty-first century—no doubt about it.

        The next question is how to think about this question. That is the business of this little book.

  • http://www.yale.edu/perception/ Brian Scholl

    Thanks to Rob for highlighting this work, and saying some nice things about it, and asking these important and interesting questions.

    Rob asks: Why is there no explicit reference in this paper to the notion that the ‘wolfpack effect’ is realized in underlying neural processes in the brain? After all, we clearly think that the effect is due to brain function at some level, but we only sort of hint at that, since saying so explicitly would be unfashionable and vaguely controversial.

    Of course, the reason that we didn’t explicitly comment on the idea that this effect has a neural correlate is not its unfashionableness, but rather the reverse: everyone already knows/assumes that such effects have some underlying neural implementation — so that saying so (at least without some interesting story about the nature of that implementation) wouldn’t really tell anyone anything they didn’t already know. (In other words, saying that explicitly would violate a Gricean maxim of quantity.)

    Oh, wait: whoops, that wasn’t Rob’s question. Rob’s question was: Why is there no explicit reference in this paper to the notion that the ‘wolfpack effect’ has an evolved function? But the answer to this question is the same as the one in the previous paragraph: we didn’t comment on that explicitly because we suspect that everyone would already know/assume that to be true.

    There may be an interesting point about different subfields of cognitive science lurking here. As Rob notes, it can be unfashionable and controversial and exciting to claim an evolved function for some aspect of higher-level cognition — and being an “evolutionary psychologist” in this sense remains a somewhat edgy affair. But not so in my field of vision science: here, as far as I can see, everyone assumes and understands that essentially all of perception serves a suite of evolved functions. The purpose of visual perception is to recover the structure of the local environment (so as to better interact with it) from certain parts of the electromagnetic spectrum that carry useful information about it. And knowing what’s going on in your local environment is so obviously adaptive, that this doesn’t really need to be said out loud.

    Rob suggests that “It’s fine to talk about evolved function for low level stuff, like the motion sensing and object recognition systems.” But, in practice, almost nobody does talk about the evolved functions explicitly in these research areas! (“And the reason that we think that these motion-sensing circuits exist is that there is motion out in the world, and it can be important, and so our ancestors evolved circuits to reliably detect it.”) And this is also true for more specific effects; for example, stimuli that loom toward your head will automatically capture your attention, but there doesn’t really seem to be any mystery for anyone about why that function would exist.

    I would hope that the same ho-humness would apply to the wolfpack effect (and to the perception of animacy more generally). We think this work shows that the wolfpack effect arises from low-level automatic visual processing of the same sort that is involved in the perception of other more pedestrian properties such as color, or texture, or depth. And just as with color, or texture, or depth, the existence of a visual mechanism that can detect and highlight this particular property (here a particular sort of ‘predatory’ animacy) is presumably due to an equally unmysterious reason — and there is then no reason to trumpet the unmysterious. If we had explicitly commented on an evolved function, I imagine that the reaction would not be scandal, but just a yawn.

    (I see two cases where evolved functions are worth trumpeting in this field. The first is when that function isn’t obvious. In color vision, for example, it’s not interesting to suggest that we see color because the physical correlates of color exist in the world, and carry useful information about objects; everyone already assumes that. But it is interesting to suggest explicitly, as some have, that the particular response profiles of the different flavors of cones are optimized to detect ripe fruit in foliage, or to detect blood, or to detect subtle changes in skin tone such as blushing; those aren’t as obvious, and so are worth highlighting explicitly. The second is when everyone assumes that an effect *isn’t* serving a function at all, but is rather an artifact of some constraint or limitation. That’s what we did in the other paper that Rob mentioned about motion-induced blindness [MIB]: lots of people assume that MIB, like other perceptual ‘blindnesses’, is due to some underlying error or capacity limitation in visual processing, whereas we think that MIB exists because it serves a positive adaptive function.)

    So, in sum, we didn’t comment on the evolved function of the wolfpack effect because we thought that our readers would already assume/know (1) that such a function exists, and also (2) what it was — regardless of how we named the effect. This is sort of the opposite of unfashionableness, just as in the brain-talk in the first few paragraphs above: far from being edgy, that’s really just a background, ho-hum, and entirely uncontroversial aspect of the underlying theorizing in vision science. In other words, all vision scientists are basically evolutionary psychologists both in theory and practice, but wouldn’t think that is worth noting. (And wouldn’t the readers of this blog hope that the same would one day be true for the study of cognition at large?)

    • Sarah

      Such an enjoyable exchange. I think the implicit question in Rob’s original post, and the implication of Brian’s question at the end of his comment still remains:

      What lessons can we take from vision science when we attempt to explicate the structure of systems for which the evolved functions are non-obvious?

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