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International audience; Decision making under risk, i.e., choices involving benefits and/or losses, is fundamental in humans and other animals. Biologists generally aim at highlighting attitudes towards risk (i.e., risk proneness or risk aversion, for example) that would reflect naturally selected adaptations to past environmental conditions for a given species. Previous research in behavioral economics has established that various biases affect investor behavior. In this paper, we show that heuristics and biases are most likely a heritage from our evolutionary past as they are also detected in non-* Corresponding author: Marie-Hélène Broihanne, mhb@unistra.fr. Broihanne M-H. and Dufour V. 2 human primates and observed early in children. In this paper, we present our results obtained by running a similar food gambling task with children and individuals of 6 different species of non-human primates. In the experiments, subjects were given an initial reward that they could either choose to keep or gamble in a lottery. The lottery consisted of a set of six cups containing visible food. If the subjects gambled the initial reward, they received the content of one randomly chosen cup. We used combinations of rewards that were larger, identical to, or smaller than the initial (safe) one and presented them to subjects in a random ordering. Observed gambling rates were analysed in the different sets of individuals and estimations of different choice theories (Expected Utility Theory, Cumulative Prospect Theory) parameters were run. We detected and measured risk aversion and loss aversion at various levels in non-human primates and children. The key finding is that cognitive processes in the context of risk are not uniquely human and are based on biologically measurable foundations.

We analyze the presence of the disposition effect for 90 244 French individual investors based on a large brokerage account database between 1999 and 2006. Main results show that a) French investors demonstrate a strong preference for realizing their winning stocks rather than their losing ones (disposition effect).b) the behavioral bias is not eliminated for sophisticated individual investors (higher trading activity or international diversification) c) more originally, based on French account specificities, we demonstrate that the change of “fiscal account type” does not imply a change in investors’ behavior (at an individual level of the disposition effect).