Acquiring auditory and phonetic categories

Infants' first steps in language acquisition involve learning the relevant contrasts of the language-specific phonemic repertoire. This learning is viewed as the formation of categories in a multidimensional psychophysical space. Categorization research in the visual modality has shown that adults are unable to learn multidimensional categorization problems without supervision. The success of infants in acquiring a phonetic system suggests that formation of multidimensional categories should be more tractable in the auditory modality. We describe experiments investigating adult learning of multidimensional speech and nonspeech categories. These experiments revealed that the degree of difficulty is actually significantly greater than that observed in the visual modality. Despite comparable methods, our results differ from those in visual category learning: feedback that is effective for visual categories is not effective in the auditory modality. Attending to more than one dimension in auditory category formation is possible for adult listeners, but very hard