Revisiting speech rate and utterance length ... - ResearchGate

162M. Blomgren, A.M. Goberman / Journal of Communication Disorders 41 (2008) 159–178As discussed, these same two variables also serve as modulating variables for frequency ofstuttering in stuttering speakers. However, the relative importance and possible interactionbetween these (and other) motor and linguistic variables is poorly understood in stutteringspeakers. One methodology to examine possible interactive effects of these variablescomes from the motor learning literature.Gentile (1987) and others (Hautala & Conn, 1993; Magill, 2004) have demonstratedthat temporal and spatial variables are relevant to the description of non-speech motortasks (e.g., walking, hitting a golf ball, or buttoning a jacket) and they have modeledthese variables using multidimensional skill performance matrices. Within these skillmatrices, the various skill categories (or tasks) place varying demands on the performer.These skills are often classified on a continuum varying from relatively simple torelatively complex tasks. Tasks conducted at the simple end of the continuum arereferred to as closed motor skills and skills conducted at the complex end of thecontinuum are referred to as open motor skills (Gentile, 1972; Poulton, 1957). Closedmotor skills occur in a stable task environment and tend to be serially ordered,temporally stable, and spatially stable. Conversely, open motor skills occur in a nonstableenvironment, where the temporal or spatial aspects of the task change during theperformance of the task. This inter-trial variability is often the defining characteristic ofopen motor skills.As rate of speech and length of utterance have both been shown to affect stutteringfrequency, it was hypothesized that a 2 2 speech performance matrix would allow for atwo-dimensional examination of speech fluency along a continuum of speech taskcomplexity. If specific tasks vary in terms of stability of speech rate and length of utterance,this can allow for an examination of the relative contributions of temporal/motor andspatial/linguistic parameters on speech motor control. A 2 2 speech performance matrixis shown in Fig. 1. The goal of this particular arrangement of speech production tasks is tocreate a hierarchy of performance complexity ranging from a relatively closed task (a seriesof single words spoken at a stable rate) to a relatively open task (a series of phrases spokenat varying rates of speech).Fig. 1. Illustration of 2 2 performance matrix applied to two speech variables: speech rate and length ofutterance. The matrix displays a progression from a relatively closed task (series of single words produced at asteady habitual rate) to a more open task (series of phrases produced with variable rates of speech). Note: 1: closedtask; 2 and 3: intermediate tasks; 4: open task.