Abstract:

The probe-signal method was used to determine whether chinchillas listen selectively for a signal tone in the presence of continuous broadband noise. Animals ran in blocks of 40 trials: 32 trials were tone trials and 8 trials were blank trials. Of the 32 tone trials, the signal tone of 1000 Hz was presented on 24 trials; probe tones of 500 and 2000 Hz were presented on four trials each. The sound levels of the 500-, 1000-, and 2000-Hz tones were adjusted to be equally detectable, as determined from psychometric functions that were generated using the method of constant stimuli. The behavioral sensitivities as estimated by d[sup '] for the signal tone based on the probe-signal method were similar to or larger than the estimated d[sup '] based on the psychometric functions. The sensitivities for the detection of the probe tones were also similar to or larger than the sensitivities measured with the psychometric functions. The results indicate that chinchillas do not listen selectively to a single auditory filter, but rather appear to use a wide-band listening strategy. This apparent wide-band listening strategy may account for the higher detection thresholds observed in animals compared to human listeners. [Work supported by NIDCD.]