Spotted at last: "Homo economicus"?

Are we selfish? Economists like to say that, to a first approximation, we are. In other words, that we tend to seek to maximize our own rewards, in a more or less rational manner. The trouble is that this theory (at least, a straightforward interpretation of it) doesn't describe how people behave in many situations. For example, given a sum of money and asked to decide how to split it between themselves and an anonymous stranger, most people choose to give some of it away. This scenario is called the Dictator Game, and along with a handful of similar tasks, it's a problem for the selfish theory. But what if some people do behave in an economically optimal way? What if the economic man, Homo economicus does exist after all - but as a minority of Homo sapiens? This is what Japanese researchers Toshio Yamagishi and colleagues say in a new paper in Psychological Science: In Search of Homo economicus (no relation to the 2001 paper of the same name.) Yamagishi et al tested 564 adults who lived in "a relatively wealthy Tokyo suburb". The headline result was that 7% of the participants displayed "Homo economicus" behaviour both in the Dictator Game, and in the more complex Sequential Prisoner’s Dilemma. That is, 7% of people always chose to maximize their own expected payoff, regardless of how this disadvantaged anyone else. Who were these 7%? Men were somewhat overrepresented (8.5% of men vs. 5.2% of women fell into this group), and they also tended to be younger, comprising 18% of those in their 20s, but just 5% of people in their 40s. Compared to the other 93%, they also rated themselves more highly on questionnaires measuring things like 'individualist social-value orientation' and self-esteem. Remarkably, "Homo economicus" scored higher IQs than their less selfish-rational participants did - the difference being roughly 10 points.