Testing the translational-symmetry hypothesis of abstract-concept learning in pigeons.

The translational-symmetry hypothesis of abstract-concept learning was tested in a same/different (S/D) task with pairs of pictures. The translational-symmetry hypothesis proposes that subjects discriminate same trials by the simultaneous repetition of features in the two pictures (and different trials by the lack of feature repetition). Pigeons that had learned a simultaneous S/D task were tested with delays between the two pictures to remove emergent perceptual cues. In Experiment 1, we tested delays of 0 and 1 sec. The results did not show the accuracy decrease expected according to the translational-symmetry hypothesis. In Experiment 2, we expanded the delays to 2 and 6 sec. Even at the longest delay, there was no evidence of the precipitous performance decline or default strategy that would be predicted by translational symmetry. The results provide evidence against translational symmetry (or other perceptually emergent features) that might control these pigeons' performance in our two-item S/D task.