This research will provide new insight into auditory, phonetic and attention requirements necessary for speech perception. The research will study children's unique responses to speech perception tasks in order to uncover basic processing abilities of humans and in order to test theories of speech perception. In the first phase of study, ten children aged five to six and ten adults will participate in discrimination testing, labeling, and selective adaptation tasks. The selective adaptation task typically results in a shift in the location of listeners' phonetic category boundary after exposure to repeated presentations of one stimulus (the adaptor). The boundary change reflects the differing contributions of peripheral auditory, more central auditory, and linguistic/phonetic influences on speech perception. These contributing factors can be addressed by manipulation of characteristics of the adaptor stimulus used during selective adaptation trials. Because Sussman and Carney (1989) showed that school-aged children, in sharp contrast to adults, did not demonstrate a selective adaptation effect, this research should clarify whether results with children were due to children's poorer discrimination ability, different choice of best phonetic category exemplar, or attention factors. By administering different adaptor conditions to children compared to adults and comparing performance to measures of auditory discrimination, phase one will reveal the importance of acoustic, phonetic, and attention factors for speech perception. Results from the first phase of research will be expanded into a multi- year project including three sets of investigations. 1) Older children will be studied to determine if and when the relationship between lower-level auditory abilities and selective adaptation becomes adult-like. 2) Adult selective adaptation ability will be studied with a spectral match variable to further examine the necessity of attention factors. 3) Psychoacoustic and speech perception abilities of children with language impairment will be studied. Preliminary research has shown that language-impaired children have poorer discrimination abilities for speech perception than their age-matched peers, and investigation should clarify the contribution of auditory perceptual vs. linguistic factors for speech perception.
