Neuroscience, evolution, and culture

Human Cognitive Uniqueness conference videos are online!

Watch them here!

Videos and slides for Understanding Human Cognitive Uniqueness

I am starting to post videos and slides from Understanding Human Cognitive Uniqueness on the conference page. They will be uploaded as they get ready.

The videos have been recorded and edited by Malene Schjoenning.

Understanding Human Uniqueness: Full Program

The program for Understanding Human Uniqueness has been finalized and is available here. See the conference page or the invitation flyer for more details.

Cultural variation in face perception!

My cousin alerted me of this paper about the cross-cultural perception of facial expressions, by Rachel Jack and colleagues. The study uses an innovative method to uncover how we perceive facial expressions, and more specifically whether `Westerners’ (Europe, North America) and ‘East Asians’ (China, Japan, Korea, Mongolia, Thailand, Taiwan) use the same criteria.

The authors find several differences, such as that Westerners pay more attention to the lower part of the face, while East Asians to the eyes. Also, East Asians attach more significance to the immediate signs of emotion, while Westerners pay more attention to later parts of facial displays. While more work is neededd to understand the reasons for these differences (the authors have some ideas in their Discussion), the data show clear variation in how emotions are perceived (and, presumably, produced) across cultures. The implication is that our emotion recognition mechanism cannot be wholly innate, but it must be open to learning the specifics of each culture.

This conclusion agrees with the fact that other aspects of facial perception, such as the perception of attractiveness, may vary across cultures. Many years ago (on my timescale, it was 2002), some colleagues and I tried to figure out how much nature and how much nurture we should expect in the perception of attractiveness. We concluded, based on what we know about perceptual mechanisms and about the evolution of biological signals, that people’s criteria of attractiveness should be mostly learned, thus leaving space for cross-cultural variation also in this domain. The paper is here.

Method. In case your are still reading, the method employed to reconstruct the criteria of Westerners and East Asians is as follows (simplifying a bit). A computer software generates short (1.25 s) animation of faces by combining randomly selected “facial action units” (AUs), which represent how different muscles move parts of the face. These movies (lots of them) were rated by observers for intensity and quality (sadness, happiness, anger, etc.). The idea is that, although the movies show random combinations of AUs, statistical analysis of people’s responses allow the reconstruction of each AU’s role. For example, the analysis might pick up that expressions including AU 6 (raising the cheeks) are typically rated as happier than expressions without AU6.

Talking about yourself feels better if others are listening: Why?

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!

If baboons can read, can pigeons, too?

“Can pigeons read?” is the question asked at the beginning of this old video, aimed at illustrating techniques to teach animals complex discriminations by rewarding them for correct choices but not for incorrect ones.

These techniques, developed around 1930, have been used in a study teaching baboons to recognize English words from non-words. Soberly entitled “Orthographic processing in baboons,” the study has been often headlined “Baboons can read,” even by the very journal who published it. My colleague Johan Lind was delighted to hear the news: “If they can read, then I can write to them and ask about animal intelligence.” Unfortunately, the only thing the baboons would be able to tell Johan is which combinations of letters are more likely to appear in English words, which is what they learned by receiving food anytime they correctly identified four-letter sequences as an English word or a non-word.

The study actually demonstrates that you do not need to know language to tell words from non-words. All languages have a statistical signature, whereby some combinations of sounds (and, therefore, letters) are common, and others are rare. Baboons are smart enough, and see well enough, to learn this. I would not be surprised if pigeons could do it too, given that they can, for example, discriminate paintings by different artists, presumably learning something about the artists’ “visual grammar.” Pigeons can also associate different written words with different actions, as the video above shows. All this suggests that the evolutionary origin of our ability to read is even more ancient than “reading” baboons suggest, pigeons being separated from humans by some 150 million years of independent evolution. Analyzing the structure of visual stimuli is a natural task for many animals, and I do not think the key to understanding human uniqueness lies here.

Understanding Human Uniqueness Flyer

We have prepared a flyer to advertise the Conference on Human Cognitive Uniqueness that will take place at Brooklyn College on May 29-30. Feel free to use it to advertise the Conference yourself!

The Logic of Fashion Cycles

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.

New paper: The logic of fashion cycles

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.

Triple Coffee Gelato

The most common problem with coffee gelato is its consistency: adding coffee means taking out either milk or cream, which often results in a icy rather than creamy texture (even at professional Italian gelaterie). My solution is to use coffee concentrate. I use a Moka pot, the Italian standard way of making coffee in the house, and I concentrate the coffee by re-cycling the water through the machine for multiple brewing cycles, each time replacing the used coffee grounds with fresh coffee. For this recipe I use what is marketed in Italy as a “3 serving” machine, yelding about 1/2 cup of coffee. I re-cycle 3 times, hence the name of this recipe. The base gelato recipe is from here.

  • 1 cup whole milk
  • 1/4 cup sucrose and 1/4 cup glucose (why glucose?)
  • a pinch of salt
  • 1 cup heavy cream
  • 7 large egg yolks
  • 1/4 teaspoon vanilla extract
  • 1/2 cup coffee concentrate (see below)

Heat up the milk, sugar and vanilla extract in a saucepan until the sugar dissolves. In a bowl, stir the egg yolks until homogeneous, then pour the warm milk over them stirring constantly. Scrape everything back into the saucepan and cook (without boiling) for a few minutes, stirring continuously with a spatula until the mixture coats the spatula. Let cool (or not), add the heavy cream and the coffee concentrate, and pour in the gelato maker.

Variations: I often complement this gelato with toffeed nuts. Melt 1/2 stick of butter with 1/4 cup sugar and let go on high heat until the mixture starts to brown. Browning happens fast, so be on your guard. To verify that the toffee is ready, drop a drop in cold water cup. It’s ready when it solidifies into a hard lump. Then you pour the toffee on parchment paper, add the nuts (I use pecans) and let cool in the freezer to make the whole thing brittle. Mix the nuts in when the gelato is fresh out of the machine. After discovering this variation, I am not making plain coffee gelato again.