Categorization of natural movements by pigeons: Visual concept discrimination and biological motion. Journal of the Experimental Analysis of Behavior

In three experiments, pigeons were exposed to a discriminated autoshaping procedure in which categories of moving stimuli, presented on videotape, were differentially associated with reinforce-ment. All stimuli depicted pigeons making defined responses. In Experiment 1, one category con-sisted of several different scenes of pecking and the other consisted of scenes of walking, flying, head movements, or standing still. Four of the 4 birds for which pecking scenes were positive stimuli discriminated successfully, whereas only 1 of the 4 for which pecking was the negative category did so. In the pecking-positive group, there were differences between the pecking rates in the presence of the four negative actions, and these differences were consistent across subjects. In Experiment 2, only the categories of walking and pecking were used; some but not all birds learned this discrimi-nation, whichever category was positive, and these birds showed some transfer to new stimuli in which the same movements were represented only by a small number of point lights ( Johansson’s ‘‘biological motion’ ’ displays). In Experiment 3, discriminations between pecking and walking move-ment categories using point-light displays were trained. Four of the 8 birds discriminated successfully, but transfer to fully detailed displays could not be demonstrated. Pseudoconcept control groups, in which scenes from the same categories of motion were used in both the positive and negative stim