Americans: outliers among outliers

Researchers found that Americans perceive the line with the ends feathered outward (B) as being longer than the line with the arrow tips (A). San foragers of the Kalahari, on the other hand, were more likely to see the lines as they are: equal in length. Subjects from more than a dozen cultures were tested, and Americans were at the far end of the distribution—seeing the illusion more dramatically than all others.

More recently psychologists had challenged the universality of research done in the 1950s by pioneering social psychologist Solomon Asch. Asch had discovered that test subjects were often willing to make incorrect judgments on simple perception tests to conform with group pressure. When the test was performed across 17 societies, however, it turned out that group pressure had a range of influence. Americans were again at the far end of the scale, in this case showing the least tendency to conform to group belief.

It is not just our Western habits and cultural preferences that are different from the rest of the world, it appears. The very way we think about ourselves and others—and even the way we perceive reality—makes us distinct from other humans on the planet, not to mention from the vast majority of our ancestors. Among Westerners, the data showed that Americans were often the most unusual, leading the researchers to conclude that “American participants are exceptional even within the unusual population of Westerners—outliers among outliers.”

Weird.

Culture and human evolution

Edge has an excellent interview with Joseph Henrich on cultural and biological evolution.  He argues that the distinction between the two is fuzzy; he says they are inseparable but I think what he really means is that we don’t know how to separate them yet.  Although they are distinct concepts, they have feedback on each other which makes the separability difficult-to-impossible (though does not mean they are not distinct!).  To get an example of what he’s saying here:

Another example here is fire and cooking. Richard Wrangham, for example, has argued that fire and cooking have been important selection pressures, but what often gets overlooked in understanding fire and cooking is that they’re culturally transmitted—we’re terrible at making fires actually. We have no innate fire-making ability. But once you got this idea for cooking and making fires to be culturally transmitted, then it created a whole new selection pressure that made our stomachs smaller, our teeth smaller, our gapes or holdings of our mouth smaller, it altered the length of our intestines. It had a whole bunch of downstream effects.

We did not evolve the ability to make fire.  But once we were able to make fire, biological evolution took hold.  Cultural evolution drove biological evolution.  An important point that he makes is that culture and technology can only reach a certain level of richness in any given population level.  More complex societies require larger – or more connected – populations:

I began this investigation by looking at a case study in Tasmania. Tasmania’s an island off the coast of Southern Victoria in Australia and the archeological record is really interesting in Tasmania. Up until about 10,000 years ago, 12,000 years ago, the archeology of Tasmania looks the same as Australia. It seems to be moving along together. It’s getting a bit more complex over time, and then suddenly after 10,000 years ago, it takes a downturn. It becomes less complex.

The ability to make fire is probably lost. Bone tools are lost. Fishing is lost. Boats are probably lost. Meanwhile, things move along just fine back on the continent, so there’s this kind of divergence, and one thing nice about this experiment is that there’s good reason to believe that peoples were genetically the same.

You start out with two genetically well-intermixed peoples. Tasmania’s actually connected to mainland Australia so it’s just a peninsula. Then about 10,000 years ago, the environment changes, it gets warmer and the Bass Strait floods, so this cuts off Tasmania from the rest of Australia, and it’s at that point that they begin to have this technological downturn. You can show that this is the kind of thing you’d expect if societies are like brains in the sense that they store information as a group and that when someone learns, they’re learning from the most successful member, and that information is being passed from different communities, and the larger the population, the more different minds you have working on the problem.

If your number of minds working on the problem gets small enough, you can actually begin to lose information. There’s a steady state level of information that depends on the size of your population and the interconnectedness. It also depends on the innovativeness of your individuals, but that has a relatively small effect compared to the effect of being well interconnected and having a large population.

The analogy between brains and population level is a good one: in the brain, it is not the individual neurons that give rise to complex behavior, but the interactions between them.  The number of neurons determines the complexity of patterns that can be extracted from the environment.  A simple example in computer science is the perceptron; if you have one neuron, you can make a linear decision between two choices.  As you connect more and more neurons, you’re able to increase the complexity of the decision by adding another linear filter; eventually you can be arbitrarily complex, but at low numbers of neurons you’re going to be really limited in the number of patterns that you can decode.

But the level of complexity also has an impact on how we interact with each other:

In the Ultimatum Game, two players are allotted a sum of money, say $100, and the first player can offer a portion of this $100 to the second player who can either accept or reject. If the second player accepts, they get the amount of the money, and the first player gets the remainder. If they reject, both players get zero. Just to give you an example, suppose the money is $100, and the first player offers $10 out of the $100 to the second player. If the second player accepts, he gets the $10 and the first player gets $90. If he rejects, both players go home with zero. If you place yourself in the shoes of the second player, then you should be inclined to accept any amount of money if you just care about making money.

Now, if he offers you zero, you have the choice between zero and zero, so it’s ambiguous what you should do. But assuming it’s a positive amount, so $10, you should accept the $10, go home with $10 and let the other guy go home with $90. But in experiments with undergraduates, Western undergraduates, going back to 1982, behavioral economists find that students give about half, sometimes a little bit less than half, and people are inclined to reject offers below about 30 percent.

…I was thinking that the Machiguenga would be a good test of this, because if they also showed this willingness to reject and to make equal offers, it would really demonstrate the innateness of this finding, because they don’t have any higher level institutions, and it would be hard to make a kind of cultural argument that they were bringing something into the experiment that was causing this behavior.  I went and I did it in 1995 and 1996 there, and what I found amongst the Machiguenga was that they were completely unwilling to reject, and they thought it was silly. Why would anyone ever reject? They would almost explain the subgame perfect equilibrium, the solution that the economists use, back to me by saying, “Well, why would anybody ever reject? You lose money then.” And they made low offers, the modal offer was 15 percent instead of 50, and the mean comes out to be about 25 percent.

We found we were able to explain a lot of the variation in these offers with two variables. One was the degree of market integration. More market-integrated societies offered more, and less market integrated societies offered less. But also, there seemed to be other institutions, institutions of cooperative hunting seemed to influence offers. Societies with more cooperative institutions offered more, and these were independent effects.

This creates a puzzle because typically people think of small-scale kinds of societies, where you study hunter-gatherers and horticultural scattered across the globe (ranging from New Guinea to Siberia to Africa) as being very pro social and cooperative. This is true, but the thing is those are based on local norms for cooperation with kin and local interactions in certain kinds of circumstances. Hunter-gatherers are famous for being great at food sharing, but these norms don’t extend beyond food sharing. They certainly don’t extend to ephemeral or strangers, and to make a large-scale society run you have to shift from investing in your local kin groups and your enduring relationships to being willing to pay to be fair to a stranger.

This is something that is subtle, and what people have trouble grasping is that if you’re going to be fair to a stranger, then you’re taking money away from your family. In the case of these dictator games, in order to give 50 percent to this other unknown person, it meant you were going home with less money, and that meant your family was going to have less money, and your kids would have less money. To observe modern institutions, to not hire your brother-in-law when you get a fancy job or you get elected to an office is to hurt your family. Your brother-in-law doesn’t have a job now. He has to have whatever other job he has, a less good job.

Testosterone: cooperation or competition?

In my last post, I gave an introduction into a couple aspects of testosterone: how it rises and falls, and how it affects decision-making.  I forgot to mention that, neurally, it appears to act substantially through three areas of the brain: the nucleus accumbens, amygdala, and orbitofrontal cortex (OFC).  The nucleus accumbens is a major dopaminergic center, the molecule generally seen as responsible for decision-making and action selection.  Amygdala, as we all know, mediates fear and emotional responses (generally…).  The more interesting area is OFC, which is typically thought to be an area that is involved in self-control.  I couldn’t find many papers that I really wanted to talk about on this aspect of testosterone, so I’ll wait for another day to delve into it.

So let’s look at how testosterone affects social behavior.  In what must have been the Most Fun Study To Participate In Ever, Oxford et al. asked subjects to play Unreal Tournament in teams.  When men are playing the game against other teams, the players that contribute the most show increases in testosterone.  However, when men are forced to play against their own teammates, they have decreased testosterone!  And the subjects who contributed the most to a win showed the largest change.

But if testosterone is increasing during competition against other groups, what affect might it have on social behavior?  Eisenegger et al. used the ultimatum game, where a pair of subjects are given a small amount of money.  One of the subjects then makes an offer of part of the money to the other subject, who can either accept the money or reject it; when the second subject rejects it, neither subject gets any money.  It is well-known that people will generally reject unfair offers.  Following the framework of past studies, female subjects were given either testosterone or placebo and asked to play the game.  They found that subjects who were given testosterone made larger offers than placebo subjects.  Although the authors try to make the claim that this is because being turned down is a ‘status concern’, it could just be because they think that they will make more money that way?  Maybe this is risk-aversion?  I should also note that different study found that subjects given testosterone and asked to be the second subject will also reject more unfair offers.  But the most interesting part about the study is that the subjects who thought that they had received testosterone made much smaller offers – presumably because they already thought they knew what testosterone should do, even though they were wrong!

In a response, van Honk et al. tried using a different game.  He used the ‘public good game’ which is where all players receive 3 moneys, and can contribute some to the public good.  When at least two players contribute to the public good, all players receive 6 moneys.  Note that in this version of the game, with the contribution rate of other players, the expected value is highest when you contribute to the public good.  And subject who have testosterone administered to them give more often to the public good!  So it’s not clear whether they are being more pro-social or just smarter…

The interesting thing about this paper, though is that they also measured the ratio of ring to index finger.  This is a measure of prenatal testosterone exposure, although it doesn’t predict adult levels of testosterone.  Those with a high 2D:4D ratio (ie, those with low maternal testosterone, figure left) are most likely to contribute to the common good, and the less prenatal testosterone, the more of an effect the testosterone given to subjects has.  van Honk et al. suggest that prenatal exposure may change something physically to make subjects more receptive to testosterone, whether it is metabolism or receptor level.  They had found a similar result in a previous study which showed that suspicious individuals didn’t become any more suspicious from testosterone, but the most trusting individuals became much more suspicious when given testosterone (figure right).

The data is a bit hard to interpret, but the general feeling now is that testosterone can act as either a pro-social hormone, or one that makes you more concerned about your social status (egocentrism?).  Although I’d love to give a good clean explanation here, I cannot come up with – and have not yet found – a good unifying framework that unites all the social effects of testosterone .

References

Eisenegger, C., Naef, M., Snozzi, R., Heinrichs, M., & Fehr, E. (2010). Prejudice and truth about the effect of testosterone on human bargaining behaviour Nature, 463 (7279), 356-359 DOI: 10.1038/nature08711

van Honk, J., Montoya, E., Bos, P., van Vugt, M., & Terburg, D. (2012). New evidence on testosterone and cooperation Nature, 485 (7399) DOI: 10.1038/nature11136

Oxford, J., Ponzi, D., & Geary, D. (2010). Hormonal responses differ when playing violent video games against an ingroup and outgroup Evolution and Human Behavior, 31 (3), 201-209 DOI: 10.1016/j.evolhumbehav.2009.07.002