Common coding in pigeons assessed through partial versus total reversals of many-to-one conditional and simple discriminations

Common coding of stimuli was examined in pigeons in 3 experiments involving many-to-one mapping of lines and hues onto common events. The common events were shapes in Experiment 1 (involving delayed symbolic matching-to-sample) and food-no-food outcomes in Experiments 2 and 3 (involving simple discriminations). In Phase 2 of Experiments 1 and 2, the hue discriminations were reversed for Group Hue, the line discriminations were reversed for Group Line, and both discriminations were reversed for Group Hue-Line. Line reversals were learned faster by Group Hue-Line than by Group Line, but differences in reversal learning were not found with hues. In Experiment 3, both hue and line discriminations were repeatedly reversed until reversal transfer was stable. Relative to this baseline, significantly poorer performance was found on a line-only reversal. Overall, the results suggest that when a hue and a line are associated with a common event, both may be centrally represented as the hue.