The Role of Timing in Speech Perception and Speech Production Processes and its Effects on Language Impaired Individuals

Phoneme recognition strongly depends on the intrinsic duration of speech segments, phoneme spectral change\´s durations, and the relative timing of two overlapping events. Excerpts of fluent speech are not very well perceived below a given duration threshold, and "phonemic clauses" are signalled either by a speech pause, or the lengthening of the final word or syllable in the clause. If a sentence should be perceived as temporally fluent, changes made in the duration of one segment should be compensated by durational changes of adjacent segments. These data lead to the conclusion that temporal aspects have a primary role in vocal communication and their perception is basic for a correct exchange of information and a correct identification of the phonetic and phonologic characteristics of the vocal message. In the light of these considerations, the role that the perception of temporal phenomena plays in learning or reading language is investigated considering two theories proposed to explain reading and specific language impairments. The first theory assumes that poor readers are affected by general auditory deficits in temporal processing, whereas the second assumes that the above impairments arose from specific deficits in learning speech. Experimental data in favour of the first or the second theory are discussed, and at the light of the reported results, new experimental paradigms are suggested