Context effects in visual pattern recognition by pigeons.

In the experiments described in this paper we examined the effects of contextual stimuli on pigeons' recognition of visual patterns. Experiment 1 showed a context-superiority effect. Specifically, two target forms that were identical except for location in the visual field were not discriminated when presented alone, but the compounds formed when each of these targets was placed between a nearby pair of flanking stimuli were readily discriminated. The size of the context-superiority effect decreased with increasing target-flanker separation. In Experiments 2 and 3 the two targets differed in form rather than spatial location and were readily discriminated in the absence of flankers. Under these circumstances, adding an identical pair of flankers to each target resulted in a context-inferiority effect; this is, the two target-plus-flankers compounds were less readily discriminated than the targets alone. The size of the context-inferiority effect decreased with increasing target-flanker separation. The observed effects of context are predictable from the Heinemann-Chase (1990) model of pattern recognition.