Acoustic frequency discrimination in the goldfish.

The capacity of the goldfish (Carassius auratus) to discriminate between two acoustic frequencies was tested by means of avoidance conditioning techniques. The pulsed-tone method was used in which the subject had to discriminate between a pulsed single frequency and pulses of two frequencies in alternation. Sound pressure levels were kept at 0 dB re 1 μb. This is equivalent to a sensation level of 40 to 45 dB at the frequencies used. Discrimination limens (JND) were determined by the staircase audiometric method. At 200 Hz, the mean JND was 9-4 Hz (4·7 per cent difference); at 500 Hz, the mean JND was 17·4 Hz (3·5 per cent difference); and at 1000 Hz, the mean JND was 50·1 Hz (5·0 per cent difference). The JND at 500 Hz was significantly lower than at the other two frequencies tested. The standard frequencies covered the most sensitive hearing range of this species. Comparison with human frequency discrimination showed that the goldfish JND was an order of magnitude greater. The problem of the mechanism of frequency analysis in fish was discussed.