PERCEPTION OF 2-TONE COMPLEXES BY THE GOLDFISH (CARASSIUS-AURATUS)

Previous experiments on the sense of hearing in goldfish have used a s timulus generalization paradigm to investigate the perceptual dimensio ns evoked by spectrally and temporally complex sounds. The present exp eriments investigated the effects on perception of the frequency separ ation between two tones. In the first set of experiments, six groups o f goldfish were classically conditioned to a single tone and then test -ed for generalization to two-tone complexes having one frequency comp onent equal to the conditioning tone, and the other differing by 2-256 Hz. Generalization declined with increasing frequency differences up to about 32 Hz, and then increased for wider frequency separations. Th ese functions indicate that a restricted range of beat rates produces a perceptual quality that is quite unlike that of a single tone. The g eneralization function of frequency separation resembles the inverse o f the 'fluctuation strength' and 'roughness' functions for human liste ners. The second experiment investigated the effects of spectral locat ion on the perception of a 32 Hz beat rate. Goldfish were conditioned to a two-tone complex (500 and 532 Hz) and then tested for generalizat ion to single tones at various frequencies between 200 and 1200 Hz, an d to two-tone complexes having a 32 Hz beat rate but with the lower to ne component at various frequencies. For single-lone stimuli, generali zation was relatively weak but showed a peak at 500 Hz. For the two-to ne stimuli, generalization was more robust, but showed a similarly sha ped gradient centered on 500 Hz. Thus, goldfish behaved as if they had acquired information about both temporal modulation and the frequency location of the tone components. These perceptual behaviors appear to be shared with humans and other vertebrates. (C) 1998 Published by El sevier Science B.V. All rights reserved.