Using the self-select paradigm to delineate the nature of speech motor programming

Abstract

Purpose: The authors examined the involvement of 2 speech motor programming processes identified by S. T. Klapp (1995, 2003) during the articulation of utterances differing in syllable and sequence complexity. According to S. T. Klapp, 1 process, INT, resolves the demands of the programmed unit, whereas a second process, SEQ, oversees the serial order demands of longer sequences.

Method: A modified reaction time paradigm was used to assess INT and SEQ demands. Specifically, syllable complexity was dependent on syllable structure, whereas sequence complexity involved either repeated or unique syllabi within an utterance.

Results: INT execution was slowed when articulating single syllables in the form CCCV compared to simpler CV syllables. Planning unique syllables within a multisyllabic utterance rather than repetitions of the same syllable slowed INT but not SEQ.

Conclusions: The INT speech motor programming process, important for mental syllabary access, is sensitive to changes in both syllable structure and the number of unique syllables in an utterance.

Figure 1

In the case of the self-select paradigm, a trial begins with fixation stimulus presented in the center of the computer display. Shortly after, the individual is provided information pertaining to which speech response is required. In this example, the participant should prepare the response “baaabababaaa,” with the first and last /ba/ being 450 ms in duration and the second and third elements being 150 ms. Study time is defined as the interval between the presentation of a precue (i.e., “4L”) and the participant pressing the “END” key. This period is assumed to capture processes specific to INT, which should then be reflected in the latency of this interval. Following the depression of the “END” key, a variable foreperiod occurs prior to the presentation of the “GO” signal. Reaction time (RT) is defined as the interval between the presentation of the “GO” signal and the initiation of the speech task. In keeping with the approach adopted by Deger and Ziegler (2002), we used the SPL contour as a means of identifying the beginning and end of the speech segments (see text for details). The RT interval is assumed to capture the temporal demands of SEQ. Feedback in the form of the model was presented at the end of a trial. ISI = intersyllable interval.

Figure 2

Five experimental conditions were established that differentiated speech responses on the basis of INT complexity (horizontal dimension) and SEQ complexity (vertical dimension). At the INT level, simple syllables were composed of a single consonant and a vowel (CV), whereas the complex syllable began with a consonant cluster (CCCV) by a vowel. At the SEQ level, complexity was increased by (a) adding repetitions of the same syllable (CV_repetition or CCCV_repetition) and (b) including transitions between unique syllables (CV/CCCV_unique) during an utterance.

Figure 3

Mean study time (in ms) when articulating mono- and multisyllabic responses as a function of trial block. Error bars indicate standard errors.

Figure 4

Mean study time (in ms) when articulating multisyllabic responses that involve either unique syllables or repeated syllables as a function of block. Error bars indicate standard errors.