Optimal Classifier’s Independence Assumption 1 A Test of the Optimal Classifier’s Independence Assumption in Perceptual Categorization

Observers completed perceptual categorization tasks that included separate base-rate/payoff manipulations, corresponding simultaneous base-rate/payoff manipulations, and conflicting simultaneous base-rate/payoff manipulations. Performance was (a) closer to optimal for 2:1 than 3:1 base-rate/payoff ratios, and when base-rates, as opposed to payoffs were manipulated, and (b) was more in line with the predictions from the flat-maxima hypothesis than the independence assumption of the optimal classifier in corresponding and conflicting simultaneous base-rate/payoff conditions. A hybrid model that instantiated simultaneously the flatmaxima and COBRA hypotheses was applied to the data. The hybrid model was superior to a model that incorporated the independence assumption suggesting that violations of the independence assumption are to be expected, and are well captured by the flat-maxima hypothesis without requiring any additional assumptions. The parameters indicated that observers’ reward-maximizing decision criterion rapidly approaches the optimal value, and that more weight is placed on accuracy maximization in separate and corresponding simultaneous base-rate/payoff conditions than in conflicting simultaneous base-rate/payoff conditions.