Control of pigeons’ keypecking by the left-right arrangement of stimuli

Control of pigeons’ keypecking by conditionalities in the spatial arrangement of two element stimuli (designated A and B) was investigated. In Experiment 1, reinforcement for keypecking was made conditional upon the left-right location of A and B: Reinforcement was available when A was on the left and B was on the right (AB), but not on BA, AA, or BB trials. The pigeons successfully discriminated the rewarded AB configuration, but only after a stage in which a particular element in a particular location (e.g., A on left) primarily controlled pecking. Experiments 2 and 3 systematically replicated these findings and included controls to discount discrimination of the AB compound on the basis of the temporal order (e.g., A followed by B) rather than the spatial configuration of the elements. During a generalization test in Experiment 4, the elements were presented singly either in the left (AX, BX) or right (XA, XB) positions. As would be expected had the animals learned “A on the left, B on the right is rewarded,” responding on AX trials exceeded that on XA trials, and responding on XB trials exceeded that on BX trials.