THE AUDITORY ACUITY OF THE SHEEP (OVIS ARIES)
PRINCETON UNIV NJ AUDITORY RESEARCH LABS
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The audiometric function was determined for a ruminant ungulate, the sheep Ovis aries, by means of avoidance training and appropriate psychophysical procedures, taking particular care in specifying the sound stimulus. The subjects were four ewes of the Hampshire variety. For preliminary avoidance training, several supraliminal tones in the middle of the general mammalian sensitivity range were used as signal stimuli in the learning of leg flexion as a means of shock avoidance. Responses were measured by means of a circuit broken between the subjects hoof and the floor. Training was continued until the subject reached a criterion of nine avoidances out of ten consecutive presentations of tones of various frequencies, all of which were near threshold in intensity. After preliminary training, the up and down method modified limits was used to find auditory thresholds for 12 frequencies spaced throughout the frequency range of the sheep. The auditory sensitivity of the sheep, when compared with that of man, proved to be inferior in the low-and midrange, and superior in the upper range. It was found that the sheep was responsive to tones ranging from 100 cps to 40,000 cps at sound pressures of less than one dyne per square cm.
- Anatomy and Physiology