Advantages of Multiple Mating in Female Guppies
The evolutionary party line has traditionally been that males increase reproductive success by mating with multiple females, but females enjoy no such advantage or, more modestly, the advantage isn’t as great. This line has been drawn in no small part on Bateman’s early work on fruit flies. The work, and the broader idea, has recently been the subject of no small amount of discussion and debate.
So… you got any friends, big boy…?
A new paper now available online from BMC Evolutionary Biology by Miguel Barbosa and colleagues entitled “Fitness consequences of female multiple mating: A direct test of indirect benefits” addresses the question of what advantages, if any, accrue to females by mating with multiple males. In this case, the subject of their investigation was Poecilia reticulata, the Trinidadian guppy.
The terms “direct benefits” and “indirect benefits” the authors use in the title of the paper refer to two sorts of ways that a female guppy might improve her reproductive success by mating with more than one male. (Roughly this corresponds to quantity/quality of offspring. I confess I’m not thrilled with these terms here, but I’ll stick with the authors’ choices.) One type of direct benefit – having more offspring per se –could be from the increased possibility of a female having all her eggs fertilized, should the sperm from one male be insufficient. In such a case, the advantages should be apparent and measurable in the number of offspring produced (the so-called F1 generation). Indirect benefits, in contrast, come from producing offspring that have some (genetic) advantage in the F1 generation itself. That is, females don’t have more offspring, but the offspring that they do have enjoy higher fitness. For instance, suppose that multiple matings allows a female’s eggs to be fertilized by sperm that do well in competition with other sperm in the reproductive tract. Males in the F1 generation would then be more likely to have this trait, conferring an advantage, which might then be visible by comparing males from females who mated multiply with females who mated singly. This requires looking at the F2 generation.
This is exactly what Barbosa et al did. Female guppies were given their own tank, and divided into two groups. Guppies in the single mating group were allowed to mate with a male on day 1, and then allowed to mate with that same male again over the course of the next three days. Guppies in the multiple mating group similarly had access to one male for four days, but it was a different male each day. Offspring from the matings of both groups were themselves allowed to mate, producing the F2 generation.
They found that multiply mated females did enjoy greater reproductive success, as measured by the number of grand-offspring produced. Indeed, this advantage was large, greater than a factor of two. Where did the advantage come from? It was driven by advantages in the F1 generation. The authors find:
Multiply mated females produced 60% more viable F1 offspring, on average, than singly mated females…In the next generation, there were no significant differences in the reproductive success of individual F1 that had been produced from multiple versus single matings
Caption from the paper: Direct Fitness (F0 to F1). Mean number of viable offspring (F1) produced by singly or multiply mated F0 females, counting (A) all F1, (B) male F1, and (C) female F1.
So, singly mated females produced significantly fewer offspring than multiply mated females. As you can see in Figure 2, this difference between the two groups was due to the significantly greater number of male F1 offspring.
In the authors’ own words, from their findings they conclude:
Our results strongly support the hypothesis that multiple mating is adaptive, as manifested by an increase in female fecundity. We found that multiply mated females produce substantially more grand-offspring than singly mated females. However, because the reproductive output (F2) of progeny from multiply and singly mated females was not significantly different, we also showed that this fitness advantage is driven by the production of more offspring in the first generation (F1), rather than by elevating the fitness of offspring (second-generation effects).
They do not rule out the possibility that there are also indirect (genetic) benefits of multiple matings. The experimental procedures might have masked such benefits that might have been found in more natural populations.
In any case, this adds to the growing body of evidence that females benefit from mating with multiple males. To the extent that females do gain such benefits, the party line difference of a greater male advantage to multiple mating and female advantage to multiple mating, across taxa, seems to be getting even fuzzier.
Reference
Barbosa, M., Connolly, S. R., Hisano, M., Dornelas, M., & Magurran, A. E. (2012). Fitness consequences of female multiple mating: A direct test of indirect benefits. BMC Evolutionary Biology, 12(185). doi:10.1186/1471-2148-12-185
The “Health Governor”
A new little piece in Current Biology by Nicholas Humphrey and John Skolyes entitled “The evolutionary psychology of healing: A human success story,” is one paper in a Special Review issue on Evolution and Human Health. The article poses the following question about the placebo effect:
When people recover from illness under the influence of fake treatments, they must of course in reality be healing themselves. But if and when people have the capacity to heal themselves by their own efforts, why do they not simply get on with it? Why ever should they wait for third-party permission — from the shaman or the sugar pill — to heal themselves? (p. R697)
I’m fond of their answer, which can be summarized in a word that figures prominently in my own lexicon: tradeoffs. They explain the idea with what they call the “health governor,” a term used as something of an homage to Hill’s notion of a “central governor,” a proposed system that works to inhibit physical activity to reduce the chance of damage by continued exertion. Here’s the figure from the paper illustrating the idea.
The Health Governor/Captain
In the model, deployment of resources to heal are expensive, and so must be deployed based on a cost/benefit calculation. Increasing the activity of some element of the system – the immune response, for instance – carries the potential benefit of fighting off parasites, but comes at substantial metabolic costs, which must either be replaced or diverted from other uses. Just like a (political) Governor, there are budget tradeoffs that have to be made (e.g., fighting the war on drugs comes at the expense of allocations to education or health care for children.)
On the left side of the figure are inputs to the putative governor system, cues associated with threats to health as well as cues associated with current and future resources that can be deployed. In the center is the proposed computational system, weighing the threat posed, taking into account, presumably, the opportunity costs of using resources for healing. On the right are the outputs of the system, including features that carry greater or lesser costs. (In the middle is a captain rather than a governor, which seems to put the metaphor out at sea, but the point is clear.)
Note “Social support” toward the bottom of the list of inputs on the left side. The idea here is that cues that one has social support can influence the cost/benefit calculus of deploying healing resources. If I have others to help me replace additional resources that I might expend for healing, then I might increase the healing budget to a level higher than I otherwise would. Placebo effects, on this view, are various kinds of inputs to the governor system, moving around the best tradeoff between deploying healing resources and husbanding resources for other uses.
While the article itself is short, the authors work in some interesting findings. One such study that caught my attention is some work on Siberian hamsters. (These critters seem to show up in research with some frequency.) In the study, researchers injected hamsters with pathogens, with different hamsters having different “beliefs” about what season it was through the use of artificial lighting. Hamsters who thought that Winter Is Coming (in fine Stark fashion) husbanded resources while those who thought summer was nigh showed greater immune responses. In humans, Humphrey and Skolyes report work showing that an injection the patient can’t see reduces pain only half as much as an injection the patient can see.
So, the answer to the question I began with is that just because healing is possible doesn’t mean that it’s a good idea, given the price tag of healing. Optimal healing, as it were, depends on the costs and benefits of the different options. Further, as illustrated in the figure, these costs and benefits might depend on many factors, including the nature of the threat, reserves, the social world, guesses about the future, and so on. Optimal healing is likely to be, in a word, complicated.
It might seem slightly odd to have pain as an output on the right side, particularly because it doesn’t seem like (the phenomenology) of pain is costly. But there are costs in the form of all of the activities that the pain discourages or makes impossible. In that sense, pain can be thought of as carrying opportunity costs, whatever the benefits would be of the actions that could be taken without the experience of pain.
Readers of this blog might be interested in other articles in the Special Issue, and I’ll be saying more about tradeoffs, phenomenology, and opportunity costs soon.
Guns, Germs, & ‘Skeetos: Human Activity-Related Selection Pressures
Antibiotics are, of course, wonderful things, and countless lives have been saved because of their widespread use. However, it has been known for some time that their use carries a potentially important long term cost for reasons that are likely to be familiar to most readers. If one imagines a population of pathogens in which there is heritable variation in the degree to which they are resistant to a particular antibiotic, then individuals that carry the relevant genes for resistance will be favored relative to non-resistant strains. Using the antibiotic, then, sets up a selection pressure for resistance to the antibiotic. A great deal of ink has been spilled about this ongoing important public health problem.
However, other sorts of selection pressures humans produce are not as obvious. A recent paper in the Proceedings of the Royal Society B by Ciuti et al. is a case in point. They report some data from a study of an elk population (Cervus elaphus) in Alberta, Canada. These elk risk being killed by hunters (the guns, in the title, see?), who number a couple of dozen per day during the weekends of hunting season. The researchers put GPS collars on 122 elk, allowing them (the researchers, not the elk) to investigate if differences among elk predicted the likelihood of their being killed by hunters. (The authors use the term “harvested” to refer to what happened to about a quarter of the elk in their study, as opposed to the 97 that survived.)
In particular, the authors discuss two sorts of anti-predator strategies that an elk might use: “shy hiding” versus “bold running.” They find that the bold running strategy tended to end poorly for the elk. Animals that moved faster and stayed in open areas were more likely to be harvested. As the authors put it:
Males that were harvested responded to hunters by moving faster than elk that survived, especially during weekends, close to roads and in flatter terrain. Flatter terrain is generally more accessible to hunters, while using sloped terrain gives an ungulate a better vantage point from which to watch for predators. Thus, males that were harvested had adopted exactly the movement strategy that would increase their detectability where and when the probability of being spotted by a hunter was higher (p. 6).
Given that humans have been hunting elk for some time, why haven’t elk populations already been pushed to the shy strategy? The authors speculate that this is due to new hunting technologies. Perhaps bold running wasn’t a bad strategy when weapons couldn’t kill accurately from such long distances, but now the best strategy is to avoid being seen as opposed to avoid being close. The systematically higher rate of death among bold elk, then, is not unlike the systematically higher rate of death among non-resistant strains of pathogens. In both cases, human activity is sculpting the traits of our fellow species.
In some ways, then, human-produced selection pressures are something of an uphill battle. It was cases like this that led my former graduate student Marc Egeth and me to think about trying to roll the ball downhill, using human-produced selection pressures for good rather than for ill. In a paper recently published in the online journal that hosts this blog, Evolutionary Psychology, we wondered aloud about such a case.
Millions of people are infected with Plasmodium, the parasite that causes malaria, which is transmitted by mosquitoes. Suppose the power of selection could be harnessed to give those mosquitoes who prefer not to bite humans an advantage over human-preferring mosquitoes.
The technical obstacles might be insurmountable, but we were interested in the general idea. Suppose that mosquito populations are limited by the amount of standing water available as opposed to the amount of blood female mosquitoes can acquire. If one could give mosquitoes blood from feeders (as opposed to from people, who take various measures to defend themselves and kill attacking mosquitoes), then you could give an advantage to feeder-preferring mosquitoes, potentially selecting for the preference. The key point is, of course, to harness the power of selection rather than fighting it, as we’re doing with antibiotics.
And, yes, we recognize that the scenario we’re suggesting has an odd resonance with the plot line of True Blood, in which vampires drink blood-substitute so they don’t need to feed on humans to survive and reproduce.
Anyway, are there other ways that we can establish human-produced selection pressures to bring about positive outcomes? Maybe. My guess is that there are many cases not unlike the elk example where human activity is already systematically affecting species in ways that we haven’t yet realized or, at least, measured. (Something I wondered about recently: could size restrictions on the fish that one must throw back when one is fishing be selecting for smaller fish or slower growth? Anyone?)
References
Ciuti, S., Muhly, T. B., Paton, D. G., McDevitt, A. D., Musiani, M., and Boyce, M. S. (2012). Human selection of elk behavioural traits in a landscape of Fear. Proceedings of the Royal Society B. doi: 10.1098/rspb.2012.1483
Egeth, M., & Kurzban, R. (2012). Artificial natural selection: Domesticating the mosquito. Evolutionary Psychology.
Immoralistic Chimps
Hello, and welcome back. Yes, it’s been some time since I added a post to this blog, so thanks for checking back in. I had a somewhat frantic summer, and the rigors of travel (and a pair of week-long holidays, I confess) left me with no time to devote the proper attention to the blog, but I plan to resume now that the academic semester is set to begin here in the U.S. I will also add a couple pictures from my summer to add to the excitement of the resumption of posting. I received some suggestions for posts over the summer, and this is my thanks for the suggestions, my apology to those of you who had good ideas while I was away, and my invitation for suggestions now that I’m back.
And, yes, I know that “immoralistic” isn’t a word.
Anyway, jumping right in, an article published online in Proceedings of the National Academy recently caught my attention, entitled “No third party punishment in chimpanzees,” by Riedl et al. (Before I go any further, here is a picture of some bears. See Figure 1.)
Figure 1. Bears
In the studies reported, the authors distinguish between two different kinds of punishment. The first kind is vengeance, harming an individual who previously harmed the punisher. The second kind is third party punishment, harming an individual who harmed a third party.
To look at this, Riedl et al. presented chimpanzees with situations in which another chimp took food from the focal chimp, after which, a rope could be pulled to open up a trap door, causing the thief’s food to fall down and away, out of reach. In these second party treatments, when the punisher was dominant to the thief, chimps punished about 40% of the time. In the relevant comparison treatment – when chimps could pull the rope to punish an individual who had stolen from a third chimp – chimps punished about half as much, around 20%: an amount similar to (and not significantly different from) how often they pulled the rope in control conditions in which no theft had taken place. The authors conclude that “chimpanzees do not punish third-party violations of cooperative behavior)” (p. 3).
I think this work is interesting for a number of reasons, but the principle reason is the distinction between 2nd and 3rd party punishment. In some ways, explaining 2nd party punishment from an evolutionary standpoint isn’t all that difficult. If you and I interact many times, then if I harm you when you harm me the first time – and if you infer that I’m likely to respond to similar harms in the future with a similar reaction – then you’re less likely to harm me a second time in order to avoid my vengeance. The logic of deterrence suggests that organisms in ecologies with repeat interactions – in addition to additional constraints – might be expected to be vengeful because of the benefits of teaching others the costs of harming oneself.
Third party punishment, imposing costs on those who have harmed a third party, is the subject of considerable debate in the literature on humans. The deterrence argument is more difficult to make when the harmed individual is not the individual doing the punishing. The deterrence argument is more difficult still to make to the extent that third parties impose costs on individuals who have not harmed third parties. To take one of my favorite examples, punishing people who have sex with corpses maybe deters people from having sex with corpses, but it’s not clear how I – or anyone – is better off with less corpse-sexing going on.
Fig. 2. RK: Treehugger.
The distinction is also important in the context of multi-party interactions. Take, for instance, Toshio Yamagishi’s classic study published in 1986 – “The provision of a sanctioning system as a public good” – in which subjects could pay a cost to impose a penalty on the lowest contributor to the public good in the group they were in. (See also Ostrom et al., 1992). Is paying for punishment in such studies revenge, imposing costs on an individual who could have contributed to the public good but chose not to? Or, on the other hand, given Yamagishi’s finding that there’s more contributing to the public good when sanctioning is possible, should punishment in public goods games be assumed to be more like third party punishment, insofar as the low contributor also harmed – or, at least, didn’t help – the other two members of the group? Careful methods are needed to distinguish these possibilities (and see work by Jeff Carpenter and colleagues for a good example.)
In any case, the present study suggests that chimpanzees, unlike humans, might not be moralistic punishers, imposing costs on individuals who have harmed a third party. A continuing mystery is why humans are.
References
Ostrom, E.,Walker, J., & Gardner, R. (1992). Covenants with and without a sword: Self-governance is possible. American Political Science Review, 86, 404–417.
Riedl, J., Jensen, K., Call, J., & Tomasello, M. (2012). No third-party punishment in chimpanzees. Proceedings of the National Academy of Sciences.
Yamagishi, T. (1986). The provision of a sanctioning system as a public good. Journal of Personality and Social Psychology 51(1), 110-16.
Away from my blog.
I’ll be traveling for some time, so, unfortunately, I won’t be updating the blog for a while, but I will begin posting again when I return. I hope everyone is enjoying their summer. Here is a picture summarizing my time in Alaska. Thanks for your recent comments and suggestions for posts. They are all much appreciated. — Rob Kurzban
Special Issue of Philosophical Transactions: Some “New” Thinking About Evolution and Cognition
The August issue of the Philosophical Transactions of the Royal Society B features a set of papers around a common theme, some or all of which will likely be of interest to at least some readers of this blog. The issue title is “New thinking: the evolution of human cognition.” Cecilia Heyes and Uta Frith are credited with having compiled and edited the papers.
The theme is introduced by a lead article by Heyes — which I’ll discuss briefly here — informing readers about what is new about the way the authors are thinking about the evolution of human cognition. In particular, the abstract advertises that this new thinking “adopts a more multi-disciplinary approach than earlier ‘Evolutionary Psychology,’” and “accords crucial roles to cultural evolution, techno-social co-evolution and gene–culture co-evolution.”
In the introductory section, Heyes begins to sketch the light between Evolutionary Psychology and the new thinking:
Over the past 25 years, research on the evolution of human cognition has been dominated by a type of evolutionary psychology promoted most prominently by Cosmides and Tooby. This framework, which I will identify using initial capitals (‘Evolutionary Psychology’), is sometimes known as the ‘Santa Barbara school’ or ‘high church evolutionary psychology’. It suggests that the human mind consists of a large collection of computationally distinct ‘modules’. Each of these modules is a way of thinking that was shaped by natural selection to solve a particular type of problem faced by our Stone Age ancestors… The alternative view, the ‘new thinking’ that runs through this theme issue, sees the human mind as more like a hand than a Swiss Army knife.
First, and probably least importantly, I think referring to EP with the term “high church” is supposed to recruit the intuition of zealotry, even narrow-mindedness. Church, to scientists, after all, is regarded as a place of anti-scientism, and adding “high” suggests extremism. My own view is that this sort of terminology – which Heyes is not alone in using in the Special Issue – edges uncomfortably into name-calling. (I find “Santa Barbara school” less irritating, but it could be that as an alumnus, I’m biased, and people at other institutions who played a role in the field’s founding might well feel differently.)
More importantly, and holding aside the fact that this glosses modularity incorrectly — evolutionary psychologists use the term (I feel comfortable, ahem, asserting) to refer to specialization in information-processing, not “a way of thinking” – the key point seems to be that Heyes wants to update EP, substituting a new metaphor to show the distance between EP and the new bottles “new thinking.”
The hand, she says, is different from the knife because the hand “has a deep evolutionary history,” and “is also capable of performing a wide and open-ended variety of technical and social functions…a vast array of tasks that natural selection did and did not ‘foresee’.” The Swiss army knife can, just like a hand, also perform a lot of different tasks, including ones the original designers did not foresee, as in a recent case in which the battery cover of my cell phone was jammed shut. The hand metaphor is, I concede, a little different, in that it doesn’t capture the key insight behind the Swiss army knife, that it bundles different functional elements together.
Anyway, following these introductory remarks, the next three sections of the paper pose questions: When, How, and What. I’ll just hit a few highlights from each of these sections.
The central point of the first of the three – “When?” – is that the “new thinking…requires a much longer historical perspective” than the focus on the Pleistocene and, in consequence, emphasizes comparative work with other species. This claim is supported with reference to work that, among other things, addresses when in the course of evolutionary history certain traits evolved. Certainly comparative work is important for people who ask such questions; as someone who is interested in the design of the human mind as opposed to questions about the temporal trajectory of cognitive traits, I find such work interesting as a consumer, and it could be that such work informs hypotheses about the design of the mechanisms that I and people like me study. Indeed, this might explain why evolutionary psychologists read the animal behavior literature a great deal more, in my experience, than people who study human behavior from a non-evolutionary perspective.
The next section – “How” – asserts the following:
Evolutionary Psychology sometimes gives the impression that new cognitive processes appeared suddenly and fully-formed as a result of lucky genetic mutations and fierce, unimodal selection pressures.
This claim, softened by the way it is put, as, sometimes giving an impression, is uncited and, it seems to me, frankly, false. I can’t think of any evolutionary psychologist suggesting that new mechanisms appeared “suddenly and fully-formed,” and I look forward to Heyes providing documentation of this bold assertion. One claim that she does cite is a point about a key difference between EP and the “new thinking”:
In contrast to Evolutionary Psychology [21], new thinking about the evolution of human cognition assigns an important role to cultural evolution.
In the cited chapter (21), Sperber presented some arguments regarding the specific way in which Dawkins uses the concept of “memes” to understand culture. In particular, Sperber is worried about Dawkins’ claim that memes spread by imitation, but Sperber’s point is not that this worry means that one ought not care about cultural change. Indeed, Sperber writes:
Memetics is one possible evolutionary approach to the study of culture. Boyd and Richerson’s models (1985, Boyd this volume), or my epidemiology of representations (1985, 1996), are among other possible evolutionary approaches inspired in various ways by Darwin.
I don’t want to get too deeply into the minutiae here, and the issue of the citation per se isn’t exactly the point. But this quote illustrates that Sperber thinks that Darwinian approaches to culture are sufficiently important that he himself has such an approach.
Moving right along, in the last substantive section, Heyes writes:
Evolutionary Psychology suggested that, in contrast to our primate relatives, we have a range of distinctive, special-purpose cognitive gadgets or modules, each responsible for thinking about a particular kind of technical or social problem that confronted our Stone Age ancestors. Experience was assumed to play a limited role in the development of these modules.
I think this gloss of modularity is, again, more or less wrong, but the second sentence there strikes me as an especially poor characterization of the discipline. (A similarly peculiar view of EP’s view of development is in another of the articles in the issue. Shea writes (my emphasis) “Evolutionary Psychology aims to account for the distinctive features of human life by appealing to special-purpose psychological capacities that have exactly those features: they are prototypically the result of gene-based natural selection, do not depend upon learning for their acquisition (and so admit of a poverty of the stimulus argument), are relatively developmentally fixed and hence culturally universal.”)
In all of the representations of the field with which I’m familiar, the commitment to the view that mechanisms develop through interaction with the environment – experience – is explicit. To be sure, experience is structured by learning mechanisms, but experience plays a key role. To take but one example, Tooby and Cosmides, 1992, in their discussion of learning, write: “the problem of learning ‘culture’ lies in deducing the hidden representations and regulatory elements embedded in others’ minds that are responsible for generating their behavior.” (p. 118)
The rest of the third section describes a view which seems perfectly compatible with the way that I, at least, think about development, but I didn’t read the other articles in the issue that she cites here, so perhaps there is something genuinely new about the new thinking.
So, to summarize, the “new thinking” differs from EP by using a different metaphor (hand instead of knife), emphasizes comparative work, emphasizes cultural change and assigns a role for experience in development.
But my sense is that the new thinking isn’t, really, all that new. I mean, I suppose the hand metaphor is different, but I am skeptical it will turn out to be an improvement. The fact that the annual meeting of HBES was joint with the Animal Behavior Society seems to be a pretty good signal that the community is interested in comparative work. (Would a joint conference with animal folks even occur to the other groups that study human social behavior, such as the Society for Personality and Social Psychology? Maybe.) Many evolutionary psychologists and people in neighboring disciplines study culture and cultural change, and it seems to me we all more or less agree that development of computational devices depends on input from the (social) environment.
I confess I didn’t read the papers assembled in the special issue, though I hope to, and even if the general approach isn’t new, I have no trouble believing that there is nonetheless much to be learned from the collected papers.
References
Sperber, D. 2000 An objection to the memetic approach to culture. In Darwinizing culture: the status of memetics as a science (ed. R. Aunger), pp. 163–174.Oxford,UK:
Tooby, J. & Cosmides, L. (1992). The psychological foundations of culture. In J. Barkow, L. Cosmides, & J. Tooby (Eds.), The adapted mind: Evolutionary psychology and the generation of culture.New York: Oxford University Press.
Strong Disgust
In a previous post, I wanted to call attention to the way that people have used the word “strong” in the context of the term “strong reciprocity” by applying the same style of reasoning to fear. A key issue in these discussions is why people show a particular pattern of behavior even when the behavior can’t, as a matter of fact, have the effect for which it was selected. Why be nice in one shot games, given that reciprocity is impossible? Why be afraid of the projected image of a cave troll, given that the image of the cave troll poses no real threat?
A new paper available online (pay wall) in Evolution and Human Behavior by Stephen Ryan and colleagues that speaks to a similar issue for disgust, making a fairly strong claim in the title: “Facial disfigurement is treated like an infectious disease.” The paper reports some research by a team in Australia – including, full disclosure, some friends of mine – and speaks to the question of why people show disease-avoidance behaviors even when they “know” that the person in question can’t communicate disease. Why avoid coming into contact with something that isn’t, as a matter of fact, likely to be contaminated?
The spirit of this work has ties to my Penn colleague Paul Rozin’s famous and fun work in which he asked subjects to do things like drinking from a glass of water into which a sterilized cockroach had been dipped. Even though subjects “know” the water is safe, there’s a certain, understandable, reluctance.
Ryan et al. had people come into the lab to perform what was ostensibly an imitation task. Subjects watched a video of a person interacting with some objects, such as placing a snorkel in their mouth. The task was to do just what the person in the video did with the object. Crucially, some of the models the subjects viewed had been made up to look like they had the flu – and were therefore presumably contagious – or made up with a very visible birth mark (a “port wine stain”) on their face. The question was, even though the birth mark doesn’t indicate the presence of an actual contagion, would subjects who saw this model be less willing to put the snorkel in their mouth?
Figure 1 from Ryan et al
Briefly yes. (See their Figure 1.) People treated artifacts handled by the model with the birthmark the same as they handled the artifacts from the person who looked like they had the flu.
The explanation, which is likely familiar to many readers of this blog, draws on basic decision theory. The design of psychological systems should reflect the fact that they need to maximize expected value, not percent correct. In the case of contagion, because the cost of a miss is high – that is, coming into contact with a potentially pathogen-infested object – the system seems to be designed to shy away from contact with things that have themselves been in contact with people who deviate from the healthy phenotype even when there is good evidence – in this case, one’s knowledge about birth marks – that the origin of the deviation means that it is more or less safe to do so. Because the cost is high, the experienced low by non-zero probably directs the subject away from the “risky” behavior.
Importantly, to connect back up to the point above, subjects showed similar amounts of disgust expressions in the birth mark conditions, and, further, subjects knew – that is, reported explicit knowledge that – the people with the birthmark posed no special threat of contagion. In the authors’ own words:
Consistent with our prediction, participants demonstrated disgust at the prospect of contacting props touched by the birthmark and influenza confederates, and avoided contact with these props especially when the contact was more intimate (i.e., face, mouth). These reactions to the confederates with influenza and a birthmark would seem to be implicit because, when asked at the end of the study, participants reported influenza as being more contagious (M=6.4 vs. 1.3) and more lethal (M=3.7 vs. 1.4) than a birthmark. Thus, even though participants knew the birthmark confederates were noncontagious, they responded to them as though they were and in a largely identical manner to the confederate with an infectious disease.
So, do people show “strong disgust,” avoiding contact with objects even when they “know” that there’s no particular contagion risk? Apparently so.
Reference
Ryan, S., Oaten, M., Stevenson, R. J., & Case, T. I. (in press). Facial disfigurement is treated like an infectious disease. Evolution & Human Behavior.
Are Hungry People More Liberal?
A recent news story about a finding about the neuroscience of “self-control” ventured that the reason that someone “who works very hard not to take seconds of lasagna at dinner winds up taking two pieces of cake at desert” was that the person had used up their mystical and mythical self-control resource. Call me crazy, but it seems to me that an alternative – dare I say simpler? – explanation would be that the person who didn’t take a second helping of lasagna was still hungry when the desert tray appeared. Similarly, one need not posit a resource to explain why hungry judges are more punitive or hungry people are less patient. Generally, as organisms get hungrier and hungrier, we should expect their behavior to change, prioritizing acquiring food over other tasks, taking greater risks to obtain food, and, of course, when food is available, eating more of it.
Hmmmm....
One talk at the HBES conference I discussed in a recent post presented some research that extended this idea in an intriguing new direction. Michael Bang Petersen and colleagues reasoned as follows. As people get hungrier, they ought to adopt strategies that will aid in either acquiring food from others coercively – showing more aggression, selfishness, etc. – or acquiring food from others voluntarily. In modern environments, one way that people can increase the chance of receiving aid from others is through the welfare machinery of the state. (This might be a good time to mention that the lead author on the study, Petersen, is at Aarhus University, Denmark…) So, the authors reasoned, maybe hungry people will be more favorably disposed towards policies that result in wealth transfers than people who have recently eaten.
This strikes me as something of a bold prediction. After all, people’s positions on particular political issues are supposed to be more like traits than states, reasonably consistent features of the person, driven by, if one believes political scientists, their ideological commitments and so forth. Further, if we take people’s policy position to be an expression of where their interests lie – a big “if,” of course, and one I’m not defending – then it would be odd that people’s positions changed based on their temporary state, given that their longer term interests aren’t changing as they go from being sated to hungry over the course of the day.
To look at this issue, Petersen and colleagues report a series of studies, one of which strikes me as particularly clever. They looked at data collected as part of the Danish National Election online survey which, because it was administered online, contained a field that indicated when the survey was taken. They looked at several hundred responses from people who took the survey between 11 and 12 – and so were between meals – compared to data from people who took it between 1 and 2 – right after, presumably, the respondent had eaten. Specifically, they compared agree/disagree responses on items such as, “Too many get social welfare without needing it.” After controlling for a set of variables – age, income, etc. – they find that, indeed, hungry people have more pro-welfare views. The authors replicated this finding in an additional survey using a similar method, and then conducted a third study in which they directly asked people how hungry they were, to see if they would find the same effects, which they did.
This is obviously a first step in a new direction, but the work strikes me as interesting and innovative. My guess is that hunger is a much better explanation for a set of effects that others have attributed to “depletion,” and I look forward to seeing more work pursuing this idea.
Speaking of which, I should mention that there was also a very interesting poster at HBES presenting some research designed to get at a related idea. I’m probably going to mangle this horribly because while I was looking at the posters, I 1) didn’t have a pen and 2) had taken advantage of the open bar, but, if I have this right, I think that the research was designed to compare people’s moral views (in the Jon Haidt Foundations sense) during a time when food was plentiful and when food was scarce in a field site in East Africa. The prediction was, I think, that moral views would change depending on season. (The work was patiently and competently explained to me by Isabel Scott, and if I’ve butchered it, sorry about that.)
Anyway, interesting work, and particularly nice to see evolutionary approaches making additional inroads into political science.
Reference
Petersen, M. B., Aarøe, L., Jensen, N. H., and Curry, O. (2012). Social Welfare and the Psychology of Food Sharing: Short-Term Hunger Increases Support for Social Welfare.
Note: This post has been slightly updated from the original; I corrected one error, having reversed “traits” and “states” in the third paragraph. Thanks: Willem Frankenhuis.
New Doctoral Program at Oakland
I am very happy to pass on an announcement of a new PhD/MS program in psychology at Oakland University (Michigan). With permission, I am pasting it here:
The Department of Psychology (Todd Shackelford, Chair, co-editor of Evolutionary Psychology, www.ToddKShackelford.com) is pleased to announce our new PhD/MS programs in Psychology, launching Fall 2012.
We are still accepting applications for the MS program for Fall 2012. If you are interested in applying, please visit the following website for instructions:
http://www.oakland.edu/psychology/grad/admissions
If you would like additional information about our programs, please contact Dr. Virgil Zeigler-Hill (zeiglerh@oakland.edu) or visit our website:
http://www.oakland.edu/psychology/grad/
The 24th Annual Meeting of the Human Behavior and Evolution Society – Some Reflections
The 24th Annual Meeting of the Human Behavior and Evolution Society (HBES) took place last week in Albuquerque, New Mexico on the campus of the University of New Mexico. This meeting brings together evolutionary psychologists and scholars in related disciplines to present their latest research, exchange ideas, and fight over the six or seven taxi cabs that seem to be serving the entire city of Albuquerque.
This year’s HBES meeting was a first in that it was scheduled to be adjacent to the annual meeting of the Animal Behavior Society (ABS), and included one joint day of sessions and talks. I was unable to attend any of ABS except for that joint day, but overall the joint meeting seemed by and large to be a success, with at least some cross-talk among people from both groups. Bill Rice’s talk on the morning of the joint day (“A new form of intragenomic conflict between sex chromosomes”) was, to me, a particular high point of the conference.
The skeleton of HBES is a series of Plenary Addresses, one-hour sessions during which no other events are scheduled so that everyone can attend. The joint day featured a talk by Mary Jane West-Eberhart in addition to the one by Bill Rice. The other plenary speakers were Brian Hare, Laura Glylnn, Karen Kramer, Clark Barrett, and Karen Wynn. Paul Bloom delivered the keynote address on Saturday night, drawing from his recent book, How Pleasure Works, which was very well received, in large part due to Bloom’s entertaining style and the very interesting material, and in some small part due to the fact that the keynote address was preceded by three hours of open bar. Be on the lookout for Bloom’s next book, Just Babies, coming soon to a book store near you. A bonus highlight was that Rapper Baba Brinkman, who recorded “The Rap Guide to Evolution,” gave two performances, which were basically awesome.
I have attended every HBES conference since the 6th one, held at the University of Michigan in 1994 with the exception of the conference in Kyoto, Japan, which I had to miss, and I thought I’d take this opportunity to reflect a little bit on how, to me, the conference has changed over the years.
The most striking change to me is that the conference felt to me to move a little bit more in the direction of “normal science” in something like the Kuhnian sense. I say this with considerable ambivalence. In Michigan in 1994, and the conferences that followed it, there was substantial tension in the air, and not only because the conference coincided with the now famous low speed OJ Simpson car chase. (I think the bar we were in was one of the only places in the country where practically no one seemed to care about what was happening, so transfixed were we by one another’s company.) Michigan HBES had, if I dare say it, something of a revolutionary feel to it. It was ten years after the famous Macintosh ad, and my impression is that many attendees felt that they were running around the scientific landscape with sledge hammers just looking for a screen with big brother to smash.
If memory serves, many presentations, in a word, sucked. Depending on how exactly one dates the field, it was still young, which I suppose some will take to be a good reason and others will see as a flimsy excuse. Sociobiology had come out in 1975, of course, but Homicide had come out only six years previously, Buss’ BBS paper on sex differences came out a year after that, and The Adapted Mind was a tender two years old. I myself had only a year of graduate school under my belt at that point, but even so, I recall having the sense that there were a lot of rookie mistakes being made, and the ratio of data to theory was a bit lower than my personal taste. Still, it was an exciting time, and if some talks weren’t great, others were nothing short of inspiring. Also, in the conferences in the 90’s there were pickup ultimate frisbee games between the last talks of the afternoon and dinner, which I really enjoyed, and I miss a great deal. Not that you can play ultimate frisbee in the June Albuquerque sun, but the schedule has become too packed for such indulgences, I think.
I didn’t attend all the talks at HBES this year – indeed, the parallel session structure makes this impossible – but my sense was that there were few if any genuinely poor presentations. The lower bound was substantially higher, and very few talks were data-free and, I have to say, I was responsible for one of these theory only presentations, so mea culpa. At the same time, again with a couple of exceptions, my feeling was that the work was of high quality, but of high quality in a more normal-sciency sort of way. Presentations were solid, but felt more incremental than they had in the past, with a sense of taking the next step on the path instead of blazing an entire new direction. Having said that, my sense was also that the work was considerably more methodologically sound and statistically sophisticated. Overall, my sense is that there was mastery of the basic conceptual and methodological tools, which of course is to be applauded. And, of course, this is what one expects as a field matures, according to some philosophers of science.
Don’t get me wrong: there was still considerable excitement, and it was refreshing seeing such a consistent stream of high quality work. Further, there were still traces of the heady times of prior conferences, a fact, I think, helped along by the continued hysterical critiques of the field by Various People, which continue to give rise to a certain sense that we are still under siege, which in turn seems to build our groupishness in sensations of common cause. (I harbor this worry that if our critics ever tire of haranguing us by hanging silly views on us, the community will lose some of its bonhomie. But, shmeh, there seems to be little reason for worry on that score, as illustrated by my prior post…)
A few other differences caught my attention. For instance, it seems to me that, as one might expect, the field has moved in emphasis. There were still several sessions on mating, but this area has gone way beyond cross-cultural sex differences into more complex and subtle effects, such as systematic variation in preferences depending on hormonal changes associated with the ovulatory cycle. There was only a sort of residual interest in logical reasoning and the Wason Selection Task, but a much greater emphasis on questions with an economic flavor using public goods games and trust games. Aesthetics seemed to have moved from waist-to-hip ratios to facial ratios. Life history theory and questions surrounding development and various sorts of learning mechanisms seemed to occupy a more prominent position. More people seemed interested in hormones and low level perception. And so on.
Not everything was different, of course. At one point, sitting across from two of my closest friends and colleagues that I met at that conference at Michigan, it occurred to me that neither had lost a jot of their 20-year-younger wit nor gained an ounce of weight, which I found simultaneously comforting and vaguely irritating.
In closing, my remarks above might seem somewhat negative. I want to emphasize that the changes I’ve seen over time at HBES are, really, a Good Thing. The quality of the work is now very solid. The mean is considerably higher than it used to be, and the variance is lower. Most of the work is really good. If my sense of the research presented at HBES today is different from my feelings a score of years ago, perhaps that says less about the work than about me. Further, as usual, and encouragingly, some of the very best work was that of young scholars in the field. I don’t like to indulge in shout outs because they might make others feel bad, but I thought that Annie Wertz’s presentation (“Social learning of plant edibility in 6- and 18-month-old infants”) was nothing short of superlative, a view apparently shared by the committee that awarded the postdoctoral prize. I’ll try to post about a few other presentations that caught my attention over the next few weeks.
Speaking of which, a couple of housecleaning items. First, to those of you who took the time at the conference to tell me that you enjoy these posts, thanks. I appreciate it. Second, my posting rate has slowed a bit. I moved in early June – only a half a mile, true – but, still, that process wound up eating up a lot of time. Related, several people at HBES asked me about the University of Alaska affiliation on my slides. I was deeply honored to be named the Rasmuson Chair of Economics at the University of Alaska Anchorage. I will head out to Anchorage this week, and I’ll be out there for much of the summer, continuing to work on my own projects – and finding time to post blog entries, of course – and developing projects with people in Alaska. My move out there might also slow me down a bit, and my post rate will go down further if I get eaten by a bear or trampled by a moose, so, you know, check back often to make sure I’m still alive.