Determination of Absolute-Intensity Thresholds and Frequency-Difference Thresholds in Cats

Abstract

The cat''s basilar membrane is only 2/3 the length of man''s, but its auditory-frequency range is at least 3 times as great. Behaviorally defined absolute-intensity and differential-frequency thresholds have been determined for the cat and are compared with those of man. The cat''s absolute thresholds lie well below those of man over nearly all of the frequencies to which the 2 species respond in common. The cat''s differential thresholds, however, are larger at all frequencies, but, because of the cat''s larger frequency range, the total number of discriminable steps appear to be about equal. Counts of ganglion cells and hair cells for the cat are reported and compared with counts for humans. The greater density of the cat''s ganglion cells may explain its lower absolute thresholds, but there appears to be no direct relation between ganglion-cell density and frequency discrimination. The lower density of hair cells for the cat, coupled with its shorter basilar membrane, may account for its poor frequency discrimination.