Form perception and attention in pigeons

This report selectively reviews the authors' research on stimulus control by visual forms. Most studies employed visual search of computer-generated displays, and the main behavioral measure was search reaction time. Pigeons classify simple line forms much as do humans, and there was some evidence for feature extraction, though a search asymmetry probe failed to identify several putative features. Dimensional analysis revealed a new quantitative relation between similarity and the probability of detecting a target. It also identified candidates for integral and separable stimulus dimensions. Similarity and set-size variables influenced the extent to which attention was engaged. Further studies addressed the manner in which attention is focused, revealing relationships between priming and search images. In these cases, attention to a selected form is probably driven by a top-down assessment of predictability.