Perception of periodicity strength in chinchillas

Abstract

In stimulus generalization paradigms, an animal is trained to respond to a particular stimulus, and behavioral responses are then measured to probe stimuli that vary systematically along a given stimulus dimension. Unlike discrimination tasks, responses to probe stimuli are not reinforced in generalization paradigms. A generalization gradient suggests how closely the probe stimuli are perceived by the animal to resemble the training stimulus and is consistent with the hypothesis that the animal possesses a perceptual dimension related to the stimulus dimension. Chinchillas were trained to discriminate a cosine-phase harmonic tone complex from wideband noise. Probe stimuli consisted of random-phase harmonic tone complexes and infinitely iterated rippled noises. These stimuli vary in periodicity strength as measured by autocorrelation and generate a continuum in the perception of pitch strength in human listeners. Generalization gradients obtained from chinchillas are related to the height of the first peak in stimulus autocorrelation functions, suggesting that chincillas possess a perceptual dimension related to stimulus periodicity strength. Comparison of generalization data to magnitude estimation data suggests a greater influence of stimulus envelope for the perception of periodicity strength in chinchillas than for the perception of pitch strength in human listeners. [Work supported by NIDCD P01 DC00293.]