Open Access Honors Program Thesis

First Advisor

Todd A. Bohnenkamp


Speech--Physiological aspects; Speech disorders;


For many individuals, speech is a nearly automatic behavior which requires little in the way of thinking about each step in the process. In addition, speech is variable and flexible both across and within situations (Netsell, 1982). Despite the fact that this is true for many individuals, speech is an extremely complex motor behavior that requires many different systems and structures to be functioning with one another. These three major systems that must work efficiently and effortlessly include the articulatory/resonatory, phonatory, and respiratory systems. This interaction relies on the theory of motor equivalence; where the capacity of the motor control system to accomplish the same goal or end product with considerable variation among the individual components that contribute to that output (Hebb, 1949; in Barlow, 1999).

To begin to describe speech, one must understand motor planning and this motor equivalence theory. A motor plan is simply what tells an individual’s body what to do and how to do it. These plans are endless and necessary for all possible voluntary movements, which includes speech. Numerous theories have attempted to explain the complexity of the number of components within motor programs for speech and how these programs function in an individual. There have been many studies done examining these theories and more specifically, the refractory period of a motor program. This term is used to describe the amount of time an individual has to inhibit a motor movement. It is important to examine this period because it can give researchers insight into motor speech disorders, specifically apraxia of speech.

Although there have been studies done looking at the refractory period of a motor program in speech, these studies come with some controversy. In some of the studies done, researchers had the subjects hold his or her breath prior to a speech task. This action is very artificial and it is effective to ask whether or not the results from these studies are valid. These studies have also been limited to solely manipulating utterance length and not the complexity of the speech task. Due to these limitations and validity questions regarding speech inhibition, this study was designed to determine the influence of inclusion of the respiratory system and increasing utterance complexity on speech inhibition.

Date of Award



Department of Communication Sciences and Disorders

University Honors Designation

A thesis submitted in partial fulfillment of the requirements for the designation University Honors

Date Original


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