To bet or not to bet? Decision-making under risk in non-human primates

摘要

Animals deal with predictable and unpredictable events on a daily basis. Yet our knowledge of the cognitive processes involved in decisions remains limited. We tested capuchins, macaques and orang-utans in a food-gambling task to investigate whether or not individuals estimate the chances of different outcomes. Results highlighted that gambling decisions were negatively induced by the probability of losing and the frequency of previous losses, and positively induced by the probability of gaining. Actual decisions were consistent with first order stochastic dominance. The study of second order stochastic dominance revealed that macaques were risk-prone whereas capuchins and orang-utans were risk-adverse. We detected responses comparable to the hot-hand effect, a bias found in humans. Capuchins and orang-utans exhibited probability distortion and loss aversion, which were not systematically found in macaques. Given the heterogeneity among individuals, we implemented mixture models and showed that attitudes towards risk and probabilities play complementary and different roles in the three species.