This study investigates reaction times in the fluent speech utterances of stutterers and nonstutterers under several experimental conditions. Twenty adult stutterers and twenty matched controls produced utterances of three lengths—one syllable words, polysyllabic words, and sentences—in two conditions of time pressure (high and low) and two conditions of preparation (delayed and immediate responding) in a reaction-time paradigm. Recordings were made of EMG signals from the orbicularis oris inferior and from the extrinsic laryngeal area, as well as electroglottographic and acoustic signals. Measures were made of the duration of intervals between the stimulus, the acoustical onset of voicing, the onset of laryngeal EMG activity, and the onset of lip EMG activity. The durations of subintervals between the stimulus, the three physiological signals, and the acoustic signal were also measured. The results suggest that the reaction times of stutterers and nonstutterers are both increased by longer utterances, and that the effect is proportionally greater for the stutterers. The requirement to respond with minimal preparation produced longer reaction times in both groups, particularly for longer utterances, but this finding was stronger for stutterers than for nonstutterers, particularly in the prelaryngeal subintervals. The high time-pressure condition produced an unusual pattern of responding in many subjects. The analysis of subintervals indicated that the additional time taken by stutterers in responding was located in the earlier parts of the response, particularly when the utterances were longer. The results are interpreted as suggesting that stutterers may have difficulty in the motor programming of speech behavior.
The main purpose of the present study was to test the hypothesis that persons who stutter, when compared to persons who do not stutter, are less able to assemble abstract motor plans for short verbal responses. Subjects were adult males who stutter and age-and sex-matched control speakers, who were tested on naming pictures and words, using a choice-reaction time paradigm for both tasks. Words varied in the number of syllables (1, 2, and 3 syllables) and, for the bisyliabic words, also in the number of consonants (one or more) at the onset of the second syllable, Measurements consisted of speech reaction times, word durations, and measures of relative timing of specific motor events in the respiratory, phonatory, and articulatory sub systems.Results indicated that, in spite of longer speech reaction times for persons who stutter in ' i comparison to control speakers, there was no interaction with word size, a finding that does not lend support to the abovementioned hypothesis. Word durations were found to be longer for persons who stutter, and, in addition, there was an interaction of group with word size. Both i findings were associated with longer delays for persons who stutter in the onset of upper lip i integrated electromyographic (IEMG) activity and thoracic compression, and a group effect, on the order of upper tip and lower lip IEMG onset. Findings are taken to suggest the possibility that persons who stutter may use different motor control strategies to compensate for a reduced verbal motor skill, and although the nature of this reduced skill is unknown, it is speculated that it relates to the processes involved in the integration of sensory-motor information. i i
Low-resolution transmittance and reflectance spectra of high-quality chemical-vapor deposition (CVD) diamond windows were measured in the infrared in the 2.5-500-mum wavelength range (20-4000 cm(-1)). High-resolution measurements on a window with nearly parallel surfaces show well defined interference fringes at low frequencies. By standard procedures the optical constants n and k of CVD diamond were determined, for the first time to the author's knowledge, in the far-infrared region. It is shown that a window with a large wedge angle, close to 1 degrees , does not produce appreciable interference fringes. Modeling of these results confirms that interference fringes can be avoided by use of properly wedged CVD diamond windows. This result is of considerable relevance to the use of CVD diamond windows in spectroscopic applications for which fringe suppression is a major requirement.
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