CLASSIFICATION OF FREQUENCIES INTO RANGES BY SONGBIRDS AND HUMANS

We trained songbirds and humans in go/no-go discriminations among 27 tones. In the compact discrimination, S + s formed a contiguous middle range (3080-4040 Hz), and S - s formed contiguous lower (2000-2960 Hz) and upper (4160-5120 Hz) ranges. In the distributed discrimination, S + s were spread across all 3 ranges. Songbirds acquired the compact discrimination more quickly and with higher accuracy than humans. Songbirds acquired the distributed discrimination only after much extended training; humans did not acquire the distributed discrimination. Compact groups (birds and humans) accurately classified test tones spaced 60 Hz from the training tones, but the distributed groups did not. A single reversal in discrimination between tones on the boundary between the lower S- and middle S+ ranges did not propagate to all the tones in either range. A neural network model provided an account of the classification of tones in songbirds and humans.