Newborn guinea pigs were tested to determine their ability to approach an auditory stimulus early in development. Observations of the behavior of 1-4day-old animals in a circular eight-choice maze revealed a pronounced tendency to orient toward and approach a tape-recorded signal of guinea pig vocalizations. The occurrence of approach responses was reduced to chance in animals tested with one ear occluded by wax ear plugs which attenuated but did not totally eliminate sound. The effect of monaural ear blocks was more severe than binaural blocks, which reflects the importance of binaural cues in the maintenance of approach responses to sound. In a second study, the ability of older animals, 11-31 days of age, was examined. Directional approach responses to sound were also evident at this age, and ear plugs disrupted performance only under monaural conditions. Furthermore, in animals raised from birth with monaural ear blocks but tested without ear plugs, there was a subsequent disruption of performance for at least 21 days. These results indicate the importance of binaural cues in the development of early auditory spatial responses and suggest the need for appropriate binaural experience for subsequent localization of sounds.
Six kittens were tested in a 2-choice maze to determine if they would execute directional approach responses to an auditory stimulus. Tests were done at various postnatal ages (4-10, 11-17, 18-24, and 25-31 days) and comparison was made with responses of 5 kittens tested without auditory stimulation. At the earliest ages no evidence was seen for auditory approach responses but by 18-24 days consistent approch responses were found.
Infant guinea pigs were tested in a circular apparatus for their tendencey to approach the source of auditory stimulation. A tape recording of guinea pig vocalizations was played over a loud speaker and the incidence of directional responses was noted. Even without external reinforcement there was a tendency to approach the particular stimulus used in this study within the first four days after birth. In order to determine the cues involved in infant localization, animals were tested with wax plugs inserted in one ear or in both ears. The plugs attenuated but did not totally eliminate sound entering the ear. Directional responding was reduced to chance by monaural blocking, but not by binaural blocking. Similar results were obtained with older animals eleven to thirty-one days of age. Furthermore, directional responding was impaired in animals raised from birth with monaural ear plugs, but tested without ear plugs. These results indicate that sound localization occurs early in development in the guinea pig, that binaural cues are important, and that monaural deprivation can affect subsequent responding.
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