Search

Deaf children 6-10 years of age, from oral or bimodal educational programs, were tested in 2 tasks. In the first, they were required to describe a designated picture from a set of 4 pictures so that their mother could identify the intended referent from the 4 alternatives. In the second, they studied a single picture and were subsequently required to identify it from a set of 4 related pictures. Despite greater hearing loss, bimodally educated children provided more differentiated messages than did orally educated children. Bimodally educated children also provided better reformulations of messages that were initially inadequate. Although mothers of orally educated children received inferior messages, they were as successful at selecting the correct referent as were mothers of bimodally educated children. Both groups of deaf children performed at near perfect levels on the picture recognition task, suggesting that performance differences were attributable to differential message formulation skill as opposed to differential visual processing of the referential array.

Localization responses to a speech phrase masked by white noise were obtained from infants 6, 12, 18, and 24 months of age and from adults. The masking noise was presented continuously from two loudspeakers located 45 degrees to each side of the infant. During a trial the speech phrase was presented through one of the loudspeakers. A head turn to the signal (correct response) was rewarded by activating an animated toy on top of the speaker. The intensity of the signal was varied over trials (method of constant stimuli) to determine thresholds (defined as the intensity corresponding to 65% correct head turns) at each of two levels of masking noise, 42 and 60 dBC. Thresholds for the speech signal were comparable across all infant groups for both levels of masking noise. Increasing the masking noise from 42 to 60 dBC resulted in a threshold shift of comparable magnitude for infants and adults. However, adult thresholds were approximately 10-12 dB lower than those of infants at both masking levels.

Localization responses to a broadband noise signal presented against a broadband noise masker were obtained from 12-month-old infants and adults. Two loudspeakers, one to the left and one to the right of the listener, continuously presented identical broadband maskers. On a trial, a broadband signal was added to one of the loudspeakers. Subjects were required to identify the loudspeaker producing the signal. Noise signals were either coherent (from the same noise generator) or incoherent (from an independent noise generator). Both infants and adults found it easier to locate the incoherent signals even when the two types of signals were adjusted to produce equal increments in power. Since monaural performance, after this adjustment, should be equivalent for the two cases, superior performance for incoherent signals implies that binaural processing is involved. The same result was observed in control experiments in which coherent and incoherent signals were presented over earphones to adults. These results suggest that the mechanisms responsible for binaural unmasking are operative by 12 months of age.

Children 4 to 6 years of age were exposed to repetitions of a six-tone melody, then tested for their detection of transformations that either preserved or changed the contour of the standard melody. Discrimination performance was examined as a function of contour condition, magnitude of contour change, rate of presentation, and the presence of novel frequencies. Performance was superior for transformations that changed contour compared to those that did not, for greater changes in contour, and for faster presentation rates. Melodies transformed by a reordering of component tones were no less discriminable than those transformed by the addition of novel frequencies.