The use of time during lexical processing and segmentation: A review

Speech, by its very nature, is a time-based phenomenon. Speech sounds are temporally distributed, with the presentation of one sound roughly conditioned by the fading of the previous one. In this review, three classes of models are discussed with respect to the sequential nature of speech. It is argued that the three resulting conceptions of time are linked to the type of segmentation process proposed by these models to deal with speech continuity. In the first one, lexical activation is viewed as perfectly synchronized with the temporal deployment of speech. This type of model corresponds to the traditional left-to-right (proactive) account of lexical processing. Because serious segmentation problems exist for such an approach (e.g.,car andcard are embedded incardinal), the second type of model treats word recognition as the result of a mechanism that sometimes delays commitment on word identity beyond word offset. Lexical activation, instead of shadowing the unfolding of time, lags behind it until an unambiguous decision can be made. The temporarily unprocessed information is stored in a memory buffer. In the third approach, a prosodic cue (lexical stress) contributes actively to speech segmentation and lexical processing. Every stressed syllable encountered in the signal is postulated as a word onset and thus constitutes the starting point of lexical activation. However, with non-initial-stressed words, retroactive procedures going “back in time” must be used. Finally, the use of time (including proactive, delayed, and retroactive procedures) is discussed in light of cross-linguistic phonological differences.