The Ash Twins Blog

Millet & Dewitte (2007) present evidence that altruistic behavior in humans is a costly signal of general intelligence:

Incurring a cost to help another organism does not seem to firt in the strict Darwinian framework. Many theories explaining various types of cooperation have been proposed in biology and economics (Fehr & Fischbacher, 2003; Gurven, 2004) but a theoretical explanation of unconditional altruism (defined as benefiting others at a cost to oneself, Wilson, 1976) has remained elusive to date. . .

Costly signaling theory (CST; Grafen, 1990a, 1990b; Zahavi, 1975; Zahavi & Zahavi, 1997) explains how individuals use costly behaviors to convey information about themselves. People may differ in the qualities that they possess, such as economic status or certain skills. These qualities may be partially concealed, while simultaneously being valuable to others. For instance, potential partners prefer an actor possessing a certain quality to an actor not possessing it. As a result, actors possessing an unobservable but desirable quality have an incentive to signal their quality to perceivers because perceivers are more likely to select them as a partner if they know their true type. However, actors not possessing the quality have an incentive to mimic the signal. Costly signaling theory provides a framework that explains how signals can be transmitted in a reliable way. Signal reliability is secured by making the signal costly and the signal-cost quality-dependent (Zahavi & Zahavi, 1997). Quality-dependence of the cost reflects the characteristic that the cost is smaller for individuals possessing the quality than for agents lacking it. Only those possessing the quality can afford the quality-dependent cost that the signal entails. . .

Altruistic behavior is costly by deWnition. However, it is less clear what quality altruistic behavior might be related to. Although unequivocal evidence for the link is still missing, some authors mentioned the possibility that altruism is related to intelligence and others reported data that seem consistent with our claim. . .

As mentioned above, Bliege Bird et al. (2001) found that some men of the Meriam spend their time turtle-hunting, which requires specific valued skills of the hunter. As hunting turtles is a relatively costly way of collecting food, it may serve as a costly signal of underlying qualities. Bliege Bird et al. (2001) proposed problem solving ability as one underlying quality that is needed to be successful at hunting: hunters with higher cognitive skills should be more successful at capturing turtles as they know better where they can find turtles, how exactly to catch them, etc. Providing turtles for a feast (an altruistic act) may serve as a signal for this underlying quality as the lower quality hunters are expected to fail more often on a hunt than high-quality individuals and as a consequence would not have the same success in providing turtles. Accordingly, unpublished data by Dewitte and De Cremer (2005) showed that students who had contributed much to group assignments had higher grades than those who contributed their fair share or less than their share. Furthermore, Van Vugt, Roberts, and Hardy (in press-b) recently suggested that altruism might signal intelligence as it may take brainpower to appreciate the long-term benefits of cooperation. . .

We organized a repeated public good game with four players, similar to the procedure by Millet and Dewitte (2006). Decisions were made simultaneously and involved contributing a certain amount to the provision of a public good. At the beginning of each round, all participants received an endowment of 40 points. In each round, they had to decide how much of the endowment they would invest in the public good or keep for themselves. Every point was worth 3.39 eurocent. All the points that were invested, were subtracted from their 40 points endowment. If the good was obtained (100 points, i.e., the provision point), 160 points were distributed equally across the four players in that round, irrespective of individual contributions. . .

Approximately 20 min after the game, participants received a computerized short-version of Raven Advanced Progressive Matrices IQ-test (RPM) (adapted from Verguts & De Boeck, 2002). They had to solve as many problems as possible in 15min. A recent review showed that the RPM-test is one of the best measures of general intelligence (Gray & Thompson, 2004). . .

Four participants were not considered for analysis because they did not comply with instructions. Of the remaining 169 participants 68 acted egoistically (42 men and 26 women), 59 cooperatively (41 men and 18 women), and 42 altruistically (26 men and 16 women). A two (sex) by three (public goods choice) factorial Anova revealed that RPM score was significantly affected by a main effect of public goods choice. Altruists scored higher on the RPM than egoists and cooperators. There was no difference between egoists and cooperators. . .

The evidence presented supports the possibility that unconditional altruism may serve as a costly signal of general intelligence because altruism is costly and is reliably linked to the quality ‘general intelligence’. Consistent with the Wnding that children’s intelligence predicts later socio-economic success better than parents’ attributes (Gottfredson, 2004), we assume that intelligence is an indicator of future resources. As a consequence, someone with high cognitive skills may be able to donate more in advance than someone with lower skills. As such, the cost of altruistic behavior could be quality-dependent.