Computational behavior theory and cultural evolution
Diana Tamir and Jason Mitchell of the Social Cognitive and Affective Neuroscience Lab at Harvard have just published a paper showing that people find it rewarding to talk about themselves, especially if others are listening (summarized here). Although, put it that way, you may or may not find the result astonishing, it touches upon an important issue in our understanding of ourselves: the difference between proximate and ultimate causes. Konrad Lorenz explained this difference in the fewest words when he said: the ultimate cause of a car is to travel, the proximate cause is the engine. That is, the ultimate cause is the function, and the proximate is the mechanism that achieves it.
Tamir and Mitchell show that brain areas that respond to reward (food, sex, money, etc.) are also activated when answering questions about oneself, more than when answering questions about Barack Obama (chosen perhaps for his interesting opinions, perhaps because he is familiar to everyone) or about dry facts. And knowing that a friend or relative would read your answer activated the reward areas even more. This, they argue, is the proximate cause of our obsession with talking about ourselves: it activates the reward areas of our brain.
The authors have been careful in validating their results conducting not one, but four distinct experiments. I will just mention that the participants were sure to know the answer to questions about themselves, but not to the other questions. So the reward they felt could reflect the anticipation of knowing the answer rather than the self-referential aspect of the question (we know the same brain areas respond to anticipated reward). After all, we are rewarded all our lives for knowing the answer to questions. But this is not my main point.
My main point is about the ultimate reason why we feel rewarding to talk to others (especially if they listen). In genetic evolution the only ultimate cause is natural selection. Things happen because they make organisms survive and reproduce. It is not hard to imagine potential benefits of sharing your thoughts with others: exchanging knowledge, strengthening social bonds, and so on. But human behavior has another ultimate cause: cultural evolution. What drives cultural evolution is imperfectly understood, but one way to think about it is to ask what are the `magical ingredients’ that make ideas popular. One such ingredient is, rather obviously, that the idea should be able to spread. Other things being equal, ideas that spread faster, convincing person after person to adopt them, will become more popular than slow-spreading ideas. And what is the best way to spread ideas? To talk about them! If you like talking to others about your ideas, these will have a good chance of spreading, and among the ideas you spread there will be those that make you like talking to others. Simplifying a bit, if you think `talking to others is cool,’ then you will say, among other things, `talking to others is cool,’ and others may be convinced of it and start talking to others, furthering the spread of the `talking to others is cool’ idea. If this sounds like a tongue twister, it is because cultural evolution is full of self-referential loops in the dynamics of ideas (one example, and another).
Thus we may like to talk about ourselves because of the dynamics of ideas, rather than because this tendency has been built into us by genetic evolution. Can we distinguish between the two hypotheses? Not yet, I believe, and the main reason is that neither evolutionary psychology nor cultural evolutionary theory (I don’t even have a Wikipedia link for that, but you can look here) have formulated precise predictions about how and when ideas should or should not be shared. But adapting Tamir and Mitchell’s experimental setup to test such hypotheses should be easy. So come on, theoreticians, give us a hypothesis to test!
As announced a few weeks ago, our paper “The Logic of Fashion Cycles” has been published, and is freely available on the PLoS ONE website. You can find a good summary at The National Post.
Plos ONE has accepted our paper “The logic of fashion cycles,” where Alberto Acerbi, Magnus Enquist and myself present a new theoretical model to understand fashion cycles (see my previous post on dog breeds). You can download a preprint, and here is the abstract:
Many cultural traits exhibit volatile dynamics, commonly dubbed fashions or fads. Here we show that realistic fashion-like dynamics emerge spontaneously if individuals can copy others’ preferences for cultural traits as well as traits themselves. We demonstrate this dynamics in simple mathematical models of the diffusion, and subsequent abandonment, of a single cultural trait which individuals may or may not prefer. We then simulate the coevolution between many cultural traits and the associated preferences, reproducing power-law frequency distributions of cultural traits (most traits are adopted by few individuals for a short time, and very few by many for a long time), as well as correlations between the rate of increase and the rate of decrease of traits (traits that increase rapidly in popularity are also abandoned quickly and vice-versa). We also establish that alternative theories, that fashions result from individuals signaling their social status, or from individuals randomly copying each other, do not satisfactorily reproduce these empirical observations.
I have recently attended a one-day course on data visualization with Edward Tufte and I have tried to put his advice on virtual paper in this supergraphic on the popularity of dog breeds, using AKC data (courtesy of Hal Herzog). The graph shows the popularity of 100 breeds over time (most popular breeds first), indicating the maximum in popularity and other peaks (if any). I have produced this graph as an inspiration for my ongoing work on cultural dynamics (some features are idiosyncratic to the data analyses I am making). Here are a few things I see in the graph:
What else can you see? And how to explain it? In am working, with Alberto Acerbi and Magnus Enquist on an explanation of fashion cycles based on the cultural dynamics of preferences, as foreshadowed in our previous work on how social learning influences openness to new information. The paper is now under review at Plos ONE.
Part of the Cultural Evolution Seminar Series at Brooklyn College
(Download video, 620 MB)
Abstract: Human language has no close parallels in other systems of animal communication. Yet it is an important part of the cultural adaptation that serves to make humans an exceedingly successful species. Evolutionary scholars have have converged on the idea that the cultural and innate aspects of language were tightly linked in a process of gene-culture coevolution. They differ widely about the details of the process, particularly over the division of labor between genes and culture in the coevolutionary process. Why is language restricted to humans given that communication seems to be so useful? A plausible answer is that language is part of human cooperation. Why did the coevolutionary process come to rest leaving impressive cultural diversity in human languages? A plausible answer is that language diversity functions to limit communication between people who cannot freely trust one another or where even truthful communications from others would result in maladaptive behavior on the part of listeners.
Pete Richerson‘s primary research for many years has focused on the phenomena of cultural transmission of information and the evolutionary phenomena that derive from cultural transmission. He has been especially interested in the trade-offs involved in using other people as a source of information. Even if we imagine that the cultural system of humans has been adaptively optimized by natural selection, maladaptive cultural variants can still evolve. People cannot take advantage of normally adaptive rules like “imitate the successful” without incurring the risk that the appearance of success is a sham behind which lurks a culturally transmissible pathology. Prof. Richerson has investigated such processes with mathematical models, laboratory experiments, and most recently field investigations.
Part of the Cultural Evolution Seminar Series at Brooklyn College
(Download video, 580 MB)
Abstract: A growing body of theory has begun to analyse human culture – the body of beliefs, skills, knowledge, customs, attitudes and norms that is transmitted from individual to individual via social learning – as a Darwinian evolutionary process. Just as the biological evolution of species can be characterised as a Darwinian process of variation, selection and inheritance, so too culture exhibits these basic Darwinian properties. I will present the results of a series of experiments that have simulated cultural evolution in the lab using methods from social psychology. One set of studies using the “transmission chain method” have identified a bias in cultural evolution for information concerning social interactions over non-social interactions, as predicted by the “social brain” theory of human intelligence. Another set of studies have simulated the cultural evolution of prehistoric arrowhead designs, testing hypotheses that different patterns of arrowhead variation are caused by different ways in which arrowhead designs were transmitted between prehistoric hunter-gatherers.
Alex Mesoudi is Reader of Psychology at Queen Mary College, University of London. He is a psychologist who studies cultural evolution as a Darwinian evolutionary process, similar in key respects to the evolution of biological species. Culture can consequently be studied using similar methods, concepts and tools that biologists use to study biological (gene-based) evolution. My own research uses a combination of laboratory experiments and theoretical models to simulate the processes of cultural evolution, with the aim of identifying the small-scale, individual-level cultural processes that generate the patterns and trends that are observed in human culture.
Part of the Cultural Evolution Seminar Series at Brooklyn College
(Download video, 520 MB)
Abstract: Parents often spend considerable energy in teaching children their own beliefs, a behavior that has both economical and cultural underpinnings. I will present an economic analysis that predicts that minority groups spend more effort in teaching their children, and I will apply it to empirical data on marriage patterns. The analysis predicts that individuals from smaller groups most often choose to marry within their own group, and spend more resources in transmitting their beliefs to offspring.
Alberto Bisin is Professor in the Department of Economics at NYU. He is an economist interested in the interaction between cultural and socio-economic forces, expanding economic theory that has traditionally explained human behavior as determined by cost-benefit analyses independent of one’s cultural background.
Part of the Cultural Evolution Seminar Series at Brooklyn College
(Download video, 660 MB)
Abstract: I argue that the social diffusion of specialist knowledge is contingent upon a combination of environmental and cognitive factors that make such ideas significant to the lay person and motivates their social transmission and retention. The same combination of factors, however, also engenders an incomplete comprehension of the ideas being spread. I propose a qualitative method to understand what makes specialist knowledge relevant and anticipate how lay peoplemay retain and spread such knowledge.
Stefano Adamo is Reader in Italian History and Culture at the University of Banja Luka, Bosnia Herzegovina, and fellowat the International Center of Economic Research, Turin, Italy. His research interests include the history of ideas and the cognitive theory of culture,especially the history of economic concepts (money, market, etc.) and their social diffusion.
The Internet Sex Survey Initiative (ISSI) has a new website. ISSI, of which I have been part since its inception in 2006, uses the Internet as a data source to understand sexual preferences and sexual development. So far, we have published the results of three surveys on sexual preferences, finding evidence for a critical age window during which preferences appear to develop, as well as for the influence of mother and father on sexual preferences.
Part of the Cultural Evolution Seminar Series at Brooklyn College
Abstract: Kinship and marriage systems represent the ways in which humans organize relatedness and reproduction. The work presented in this talk extends the philosophical, theoretical, and methodological foundations of evolutionary biology to the study of these aspects of human social behavior. Specifically, I use game theory to show that the evolution of monogamous marriage can be understood based on inclusive fitness theory. Results show that where resources are transferred across generations, monogamous marriage can be advantageous if partitioning of resources among the offspring of multiple wives causes a depletion of their fitness value, and/or if females grant husbands higher fidelity in exchange for exclusive investment of resources in their offspring. I evaluate the results of the model using evidence about the history and cross-cultural distribution of marriage and inheritance strategies. This suggests that monogamous marriage may have emerged in Eurasia following the adoption of intensive agriculture, as ownership of land became critical to productive and reproductive success.
Laura Fortunato is Omidyar Fellow at the Santa Fe Institute. Her research investigates theevolution of human social organization, focusing on the social norms regulating kinship and marriage. This involves understanding (i) why societies differ withrespect to these norms – for example, why some prescribe monogamous marriage, while the majority allow polygyny; and (ii) how this variation came about – forexample, whether the prevalence of monogamous marriage among European societies is simply an artefact of history, or whether itreflects ecological and/or social determinants.
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