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Am J Primatol. 1997;41(4):323-9.

Auditory behavioral thresholds for Japanese macaques using insert earphones.

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Division of Otolaryngology-Head and Neck Surgery, Duke University Medical Center, Durham, North Carolina 27710, USA.


The goal of this study was to measure behavioral auditory thresholds in four Japanese macaques. Animals were trained using food as a reward in an operant reinforcement paradigm. Stimuli were 1-s sinusoids with 10-ms rise/fall times delivered through insert earphones (Etymotic ER-1) having expandable foam eartips. The animals generally produced threshold contours similar in shape to those reported for other macaques species, except that the low-frequency thresholds may have been slightly higher in the present studies. At middle and high frequencies, thresholds fell at the lower extreme of the range previously reported in other macaque species. The possible difference in low-frequency thresholds may have been a result of either transducer and calibration differences between studies or true species variations, or both. Though somewhat limited at high frequencies, the insert earphones used in these studies offer more reliable calibrations, less susceptibility to changes in positioning with movement of the animal, and greater interaural attenuation.

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