Auditory Perception in Infancy

Because they have had some practice in hearing before birth, it is not surprising that infants have reasonably good auditory perception after they are born. In fact, for certain very high and very low frequencies, infants actually are more sensitive to sound than adults—a sensitivity that seems to increase during the first two years of life. On the other hand, infants are initially less sensitive than adults to middle-range frequencies. Eventually, however, their capabilities within the middle range improve.

It is not fully clear what leads to the improvement during infancy in sensitivity to sounds, although it may be related to the maturation of the nervous system. More puzzling is why, after infancy, children’s ability to hear very high and low frequencies gradually declines. One explanation may be that exposure to high levels of noise may diminish capacities at the extreme ranges.

In addition to the ability to detect sound, infants need several other abilities in order to hear effectively. For instance, sound localization permits infants to pinpoint the direction from which a sound is emanating. Compared to adults, infants have a slight handicap in this task, because effective sound localization requires the use of the slight difference in the times at which a sound reaches our two ears. Because infants’ heads are smaller than those of adults, the difference in timing of the arrival of sound at the two ears is less than it is in adults. However, despite the potential limitation brought about by their smaller heads, infants’ sound localization abilities are actually fairly good even at birth, and they reach adult levels of success by the age of one year. Interestingly, their improvement is not steady: although we don’t know why, the accuracy of sound localization actually declines between birth and two months of age, but then begins to increase.

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