The emergence of variance-sensitivity with successful decision rules

Experiments testing for variance-sensitivity (also called risk-sensitivity) usually offer 2 options delivering identical expected payoffs, with one option providing a constant and the other one a variable reward or delay. Animals often show a preference for the constant option when variance is in amount (variance-aversion) and a preference for the variable option when variance is in delay (variance-proneness). Variance-sensitivity is a taxonomically widespread phenomenon. Variance-sensitive foraging preferences contradict predictions derived from evolutionarily motivated models that emphasize long-term energetic benefits. We discuss a new approach of explaining variance-sensitive preferences. We hypothesize that variance-sensitivity results from decision mechanisms that are adjusted to ensure close to optimal responses to the environment. This paper demonstrates that simple decision rules ensure long-term rate maximization and exhibit variance-sensitive behavior when tested in a classical risk-sensitivity situation. We also show that behavioral patterns observed in experiments like preferences for constant reward amounts and variable time delays are produced by the decision rules. The decision rules presented here are a first step toward a decision mechanism that is psychologically plausible, is advantageous in natural foraging situations, and explains irrational behavior-like variance-sensitivity. Copyright 2010, Oxford University Press.