Visual search in pigeons: effects of memory set size and display variables.

Abstract

A visual search procedure compared memory and perceptual effects. Pigeons pecked at a target letter in a three-key forced-choice procedure. Experiment 1 varied memory set and display size. Neither had a significant effect on accuracy, and changing memory set from 1 to 2 items did not affect reaction time. However, reaction times grew longer as display size increased from 3 to 9 items (p < .005) and memory set size increased from 1 to 4 (p < .05). Experiment 2 extended memory set size to 6 and display size to 18. Four experienced subjects showed no significant effects of memory set size on accuracy or reaction time, while reaction time increased (p < .005) with increasing display size. Experiment 3 considered effects of distractor redundancy and target-distractor similarity. Mean reaction times for three experienced birds showed persisting display size effects that depended on target-distractor similarity; search was fastest for redundant distractor sets in which the items were relatively dissimilar to the target. Except for the persistence of a display-size effect, these outcomes are consistent with human data.