SHORT‐TERM MEMORY FOR RESPONSES: THE “CHOOSE‐SMALL” EFFECT

Pigeons' short‐term memory for fixed‐ratio requirements was assessed using a delayed symbolic matching‐to‐sample procedure. Different choices were reinforced after fixed‐ratio 10 and fixed‐ratio 40 requirements, and delays of 0, 5, or 20 s were sometimes placed between sample ratios and choice. All birds made disproportionate numbers of responses to the small‐ratio choice alternative when delays were interposed between ratios and choice, and this bias increased as a function of delay. Preference for the small fixed‐ratio alternative was also observed on “no‐sample” trials, during which the choice alternatives were presented without a prior sample ratio. This “choose‐small” bias is analogous to results obtained by Spetch and Wilkie (1983) with event duration as the discriminative stimulus. The choose‐small bias was attenuated when the houselight was turned on during delays, but overall accuracy was not influenced systematically by the houselight manipulation.