The auditory acuity of preadolescent monkeys.

Abstract

Within the last few years a number of investigators have studied a variety of psychological functions in the monkey-indeed, the monkey is becoming a preferred animal in audition and other fields. Yet although "hearing" is a factor in many psychological tests with monkeys, the most basic auditory function, namely, the intensity threshold, of the monkey is not very precisely known, while other important functions, such as pitch and intensity discrimination, are enitrely uninvestigated.This study is in inquiry, using a motor conditioning method, into the auditory acuity of the late-infant and pre-adolescent Old World monkey. To find the auditory acuity we determine the lower absolute intensity threshold for each of a number of representative frequencies over the audible range. One simply reduces step-wise the intensity of a tone of a particular frequency until the subject fails to respond to it. After several repetitions of this procedure, appropriate psychophysical methods are employed to fix the threshold precisely. Auditory acuity is then represented by a plot, the so-called audiogram, relating the physical energy of the tone at threshold intensity, to tone-frequency.Wendt (7) has investigated the auditory acuity of monkeys in a careful study. Most of his general conclusions are confirmed by the present study, and it is likely that Wendt's paper will remain a model for students of primate audition. Several considerations, however, make it desirable to repeat some of the earlier work. In the first place, Wendt was unable to present his results in terms of actual physical units. He was able to approximate this by comparing results from his monkeys with results from five human subjects in the same apparatus. However, one has to assume with Wendt that his human subjects possessed exactly the same thresholds as did Sivian and White's (6) human subjects whose thresholds were known in terms of dynes per cm 2 . Further, one has to assume that the apparatuses of Wendt and of Sivian and White were equivalent as to purity of tone, magnitude of intensity steps, standing waves, and the like. It is clear that it would be valuable to have at hand measurements of the physical characteristics of the stimulus with which to speak more precisely of the monkey's auditory acuity. This paper presents audiograms in terms of the physical stimulus.In the second place, the thresholds which Wendt reports might have been somewhat different if measured by more usual psychophysical methods. As he decreased the tonal intensity, Wendt termed as a threshold that intensity setting at which the animal last made a correct response. It is evident that his mean

AUDITORY SENSITIVITY AND EQUAL LOUDNESS IN THE SQUIRREL MONKEY (SAIMIRI SCIUREUS)1

“…Many investigators (Bragg and Dreher, 1969;Clack and Herman, 1963;Harris, 1943) are of the opinion that data obtained when the reinforcer is an aversive stimulus are more reliable than those obtained when the reinforcer is an appetitive stimulus; other experimenters (Stebbins, 1970a, Stebbins, 1971 These results suggest that sensory data are not influenced by the type of reinforcer used to maintain behavior during testing. The procedural difficulties and data discrepancies reported in other studies may have been a function of the reinforcement contingencies and behavior stability criteria, rather than stemming from inherent properties of the reinforcer.…”

“…One view receiving considerable support (Bragg and Dreher, 1969;Clack and Herman, 1963;Mitchell, Gillette, Vernon, and Herman, 1970;Mitchell, Vernon, and Herman, 1971) was advanced by Harris (1943). Harris pared the effectiveness of his aversive control technique with an appetitive procedure used by Wendt (1934) and concluded that aversive stimuli provide a more efficient means of conditioning behavior and collecting reliable data.…”

What Do Primates Hear? A Meta-analysis of All Known Nonhuman Primate Behavioral Audiograms

“…(Beecher 1974a;Fujita and Elliot 1965;Green 1971); Macaca fascicularis (Fujita and Elliot 1965;Stebbins et al 1966); M. fuscata (Jackson et al 1999;Owren et al 1988;Smith and Olszyk 1997); and M. mulatta (Behar et al 1965;Bennett et al 1983;Clack;1966;Clack and Herman 1963;Dalton 1968;Dalton et al 1969;Fujita and Elliot 1965;Harris 1943;Lasky et al 1999;LonsburyMartin and Martin 1981;Pfingst et al 1975Pfingst et al , 1978Wendt 1934). For the comparisons of Macaca mulatta, I modified or excluded several of the audiograms.…”

“…They used behavioral conditioning to determine absolute auditory thresholds (lowest detectable level) in chimpanzees and several species of monkeys, respectively. Researchers generally consider auditory thresholds the most fundamental measure of hearing performance (Harris 1943;Heffner 2004;Jackson et al 1999;Lonsbury-Martin and Martin 1981;Stebbins 1975), though they have also investigated other parameters of hearing sensitivity such as localization ability and frequency and amplitude discrimination in a handful of species. Here, hearing sensitivity refers solely to differences in absolute auditory thresholds.…”

Response Latencies in the Rhesus Monkey as a Function of Tone Intensity

“…But latencies also increase near the threshold. Harris (2), in his study of auditory acuity of monkeys, used this latter effect to simplify his testing procedure.…”