The use of lexical knowledge in phonetic categorisation

Lexical effects on phonetic categorisation have been taken as evidence that the listener's word knowledge inßuences phonetic processing during normal speech perception. Tbe present study examined word-nonword effects in the categorisation of word-initial and wordfinal stop consonants. Natural speech was edited to produce bilabial, alveolar and velar voicing continua. Tbe data revealed a significant word-nonword effect, such that subjects were more likely to categorise an ambiguous consonant as voiced if the voiced endpoint of tbe continuum was a word, bot as unvoiced if tbe unvoiced endpoint of tbe continuum ·was a word. Bot it was found tbat within some blocks tbere was no evidence of tbis lexical sbift. Subsequent experimental manipulations provided additional evidence that this shift is highly variable. The fact that the effect is nonmandatory provides support for tbe view tbat phonetic processing can occur independently of lexical processing.