The Influence of Short-term and Long-term Memory on the Identification and Discrimination of Non-native Speech Sounds

This study examined two possible sources of individual differences in crosslanguage speech perception, the capacity to phonologically encode speech and short-term memory span. Phonological coding was defined as the ability to encode non-native contrasts as distinct phonemes based on representations in long-term memory. Short-term memory was defined as a fixed capacity regulating the extent of encoded phonetic detail. To compare these two predictors of cross-language speech perception performance, thirty native speakers of American English were administered five tests: categorial AXB discrimination and identification (using non-native nasal consonant contrasts), digit span, nonword span (using pronounceable nonwords with nasal consonants, produced by a native speaker of English), and paired-associate word learning with word-word and wordnonword conditions. The AXB discrimination results were correlated with measures of short-term memory (digit span, word-nonword learning), phonological coding (identification), and a memory span measure mediated by phonological coding (nonword span). The results showed that almost all measures were significantly correlated with one another (+0.62 > r > +0.41), with the exception of word-word learning. The strongest predictor for the AXB discrimination test results was nonword span (r = +0.62, p < 0.01). When the identification test results were partialed out, only nonword span significantly correlated with discrimination (r = +0.54, p < 0.01). The results show an association between the discrimination of these non-native contrasts and a short-term memory capacity that interacts and relies heavily on prior linguistic experience in long-term memory.