Identification of consistent responding to auditory stimuli by a functionally "deaf" autistic child.

Although the severity of autistic children's unresponsiveness to external stimulation has been frequently reported, little empirical work has been conducted to specifically describe the nature of their unresponsiveness. The child who participated in this experiment was at varying times reported to be deaf, hard of hearing, or functionally deaf; and at other times was reported to have normal hearing. In this experiment, we measured his responses to systematically presented auditory stimuli in order to determine if there was any pattern to his responding. Two types of auditory stimuli were used: (a) white noise, consisting of most of the frequencies within the human range of hearing, and (b) the sound of a candy machine delivering candy. The results showed the following. (1) There was consistent responding to both the white noise and the candy feeder. (2) The thresholds for responding to the white noise were always consistent on a given day, but varied from day to day. (3) Responding to the candy machine stimulus always occurred at sound levels which were well below the threshold for the white noise. These results are discussed in terms of their implications for understanding autism, and in particular in terms of understanding the lack of speech development in mute autistic children.