Talking the talk, not walking the walk: The co-evolution of overconfidence and loss aversion

A puzzle for evolutionary theory is the existence of two seemingly offsetting behavioral “biases”, overconfidence and loss aversion. Overconfidence is a call to action, whilst loss aversion curbs initiative. The most prominent evolutionary explanation of overconfidence, proposed by Robert Trivers (1976), is that self-deceit arises to better deceive others. Missing from this account is why sincere messages are believed, especially given the widespread prevalence of self-deception. Moreover, if overconfidence is adaptive, why is it at least partially cancelled by loss aversion? We propose a signaling theory according to which the role of self-deception is to better inform others. Since the decision error associated with high self-belief is less burdensome for the more able, and the benefit of being perceived as able increases with ability, hardwired overconfidence is a credible signal of true ability. Evidence supports this interpretation. A further implication of signaling is that loss aversion is part of the equilibrium. It partially ameliorates the decision costs of overconfidence, but as it is usually hidden, it does not eliminate its signaling role. “Biases” are thus symbiotic—the payoff to agents from an integrated set of biases is higher than would be the case in their absence. From this perspective, Kahneman’s advice that individuals eliminate both overconfidence and loss aversion is poorly founded.