Auditory learning: Implications for speech perception

Auditory learning, an improvement of sound detection or discrimination with practice, has been used to study basic mechanisms of perceptual processing (Gibson, 1967; Goldstone, 1998; Hawkey et al., 2004) and as a tool for enhancing language skills (Tallal et al., 1996; Clopper and Pisoni, 2004; Moore et al., 2005b). It has relevance to speech perception in both these domains. Speech consists (Evans, 1992; B. Moore, 2004), at its most simple, physical level, of a series of frequency bands of acoustic energy that can be simultaneously and somewhat independently starting, changing and stopping over time. The auditory system plays an essential role in separating and enhancing the frequency and temporal components of speech and the extent to which it is successful in those tasks is partly dependent on practice. Of course, speech perception has multiple layers of complexity, but auditory learning appears to play a role in them all. A familiar example is the discrimination of similar sounding phonemes (e.g. /r/ /l/; Logan et al., 1991; Bradlow et al., 1999). Unlike native speakers of English, who learn to distinguish these phonemes during the first few months of life, native Japanese speakers learning English as a second language (L2) do not. However, they may be actively trained both to perceive and produce this nonnative contrast. Recent studies using auditory learning to enhance native language skills in typically developing (Moore et al., 2005b) and language impaired (Merzenich et al., 1996; Tallal et al., 1996) children have also reported positive outcomes on a wide range of speech perception indices.