Specification interacts with phonologic similarity to determine

complexity of pre-motor encoding during speech production

By M.A. Rogers and H.L. Storkel

One phenomenon that offers some insight into the nature of the units that are assembled during pre-motor stages of speech production is the Phonologic Similarity Effect. Similar sound structure among words has been shown to interfere with processing across a wide range of disparate tasks including tasks that do and do not require an overt speech response suggesting that the phonologic similarity effect arises during pre-motor stages of speech production and not during execution. Interference effects due to successive utterances sharing phonologic features provide one source of evidence that spoken language is assembled from sublexical units (not whole-word units) and that assembly of these units is required for speech production. The effects of phonologic similarity on speech production latencies were investigated to explore the role of segmental specification during pre-motor stages of production. Speech onset latencies were obtained as participants rapidly produced monosyllabic words in response to visual presentation. The featural similarity of word-initial phonemes among successive words was varied (shared voicing, manner, place, combinations of these features, and a control condition in which no features were shared). Initial phonemes also varied with respect to specificity from highly specified to underspecified segments based on the Feature Geometry model of Sagey (1990). Overall, the response latencies to produce words with highly specified initial consonants were longer than the latencies to produce words with underspecified initial consonants. The transition from underspecified to highly specified initial consonants yielded greater interference effects from phonologic similarity than the reverse transition. This pattern of results was strongest when two features as opposed to only one feature was shared suggesting that specification interacts with featural similarity to determine complexity of pre-motor encoding.