Tooby and Cosmides hypothesized that modern people use race as a proxy (rough-and-ready indicator) for coalition membership, since a better-than-random guess about "which side" another person is on will be helpful if one does not actually know in advance. Their colleague Robert Kurzban designed an experiment whose results appeared to support this hypothesis. Using the memory confusion protocol, they presented subjects with pictures of individuals and sentences, allegedly spoken by these individuals, which presented two sides of a debate. The errors that the subjects made in recalling who said what indicated that they sometimes mis-attributed a statement to a speaker of the same race as the "correct" speaker, although they also sometimes mis-attributed a statement to a speaker "on the same side" as the "correct" speaker. In a second run of the experiment, the team also distinguished the "sides" in the debate by clothing of similar colors; and in this case the effect of racial similarity in causing mistakes almost vanished, being replaced by the color of their clothing. In other words, the first group of subjects, with no clues from clothing, used race as a visual guide to guessing who was on which side of the debate; the second group of subjects used the clothing color as their main visual clue, and the effect of race became very small. Some research suggests that ethnocentric thinking may have actually contributed to the development of cooperation. Political scientists Ross Hammond and Robert Axelrod created a computer simulation wherein virtual individuals were randomly assigned one of a variety of skin colors, and then one of a variety of trading strategies: be color-blind, favor those of your own color, or favor those of other colors. They found that the ethnocentric individuals clustered together, then grew, until all the non-ethnocentric individuals were wiped out. In The Selfish Gene, evolutionary biologist Richard Dawkins writes that "Blood-feuds and inter-clan warfare are easily interpretable in terms of Hamilton's genetic theory." Dawkins writes that racial prejudice, while not evolutionarily adaptive, "could be interpreted as an irrational generalization of a kin-selected tendency to identify with individuals physically resembling oneself, and to be nasty to individuals different in appearance." Simulation-based experiments in evolutionary game theory have attempted to provide an explanation for the selection of ethnocentric-strategy phenotypes. Despite support for evolutionary theories relating to an innate origin of racism, various studies have suggested racism is associated with lower intelligence and