A comparative acoustic analysis of the Laugh responses of 20- and 70-year-old males.

Several studies have documented age-related changes in speech or voice characteristics, but no study has reported differences across age groups in human laughter. The purpose of this investigation was to identify, describe, and compare the measurements of five acoustic correlates of elicited, spontaneous laughter in twenty- and seventy-year-old males. Five acoustic characteristics of laugh responses including Initial Laugh Fundamental Frequency (ILFo), Mean Laugh Fundamental Frequency (MLFo), Peak Laugh Fundamental Frequency (PLFo), Duration Laugh Response (DLR), and Laugh Bursts (LB) as well as Speech Fundamental Frequency (SFF) were analyzed across groups. Statistically significant differences were found between twenty- and seventy-year-old males in ILFo, MLFo, PLFo, and in the number of laughs per minute. Older respondents produced a relatively compressed fundamental frequency range of laugh behavior and fewer laugh responses per minute. These differences are congruent with age-related changes in speech and voice but also might be explained by other physiological or sociological variables.

Effect of mouth opening on bite-force discrimination.

The purpose of this study was to determine whether different extents of mouth opening affect normal subjects' (N = 24; 12 women, 12 men) ability to discriminate differences in their interincisor bite force. Three mouth openings were selected including 50, 70, and 90 percent of maximum opening for each subject. Bite force was measured using a specially designed strain gauge scale which permitted subjects to monitor visually when their biting force equalled a preset resistance. Resistance forces of 500 and 1000 gm. were selected as standards. The procedure involved the use of a modified method of constant stimuli in which each subject was presented with a series of paired resistance settings, one at a time--the first resistance setting being the standard and the second resistance was the comparator. This paired-comparisons procedure was continued until the subjects' difference limen (DL) value (the threshold of discrimination between two forces) could be established. An analysis of variance yielded no significant differences in subjects' ability to discriminate bite force as a function of mouth opening.

Human discrimination of different bite forces.

Twenty young adult subjects were selected to determine normal baseline data of dynamic interdental bite force discrimination by use of a specially designed strain gauge instrument. The data may aid in defining the role of the periodontal ligament, temporomandibular joint and muscles of mastication in the regulation of interincisor bite force.

Intra-oral shape recognition by 138 mentally retarded subjects.

Among Ss with normal intelligence, oral shape-recognition tests have shown a relationship between articulatory ability and oral sensory integrity. This investigation explored oral sensory impairment as a possible contributory cause of the articulatory difficulties exhibited by the mentally retarded. The Florida Oral-form Recognition Measure (FORM), a task requiring the intra-oral identification of 10 geometric shapes, was administered to 138 mentally retarded Ss. Twenty Ss were retested to establish reliability. Ss were placed in groups according to etiological categories (AAMD classification) and were assigned speech ratings by a speech pathologist. Of the total sample, 86% had varying degrees of defective speech or language. Mean FORM score was 3.5, and preliminary analysis yielded significant correlations between FORM score and IQ and between speech and language rating. Further multivariate analysis with IQ held as a co-variant indicated no significant relationship between FORM score and communicative ability. This suggests caution in inferring that intra-oral shape-recognition scores reflect degree of oral sensory integrity. Perhaps a battery of oral perceptual tasks might more validly assess oral sensation-perception and aid in clarifying its relationship to speech.

Some phonemic characteristics in apraxia of speech.

The articulatory performance of 13 left hemisphere-damaged adults who presented apraxia of speech was tabulated on confusion matrices and analyzed according to error pattern. Consonants were more susceptible to error than were vowels, as were consonant clusters when compared to single consonants. No significant differences existed among error percentages for the initial, medial, and final positions. When errors were analyzed according to manner of production, affricatives and fricatives were significantly more susceptible to error than all others. Analysis of errors according to place of production revealed lingua alveolar and bilabial phonemes to be significantly less impaired than all other categories. No differences were found in error percentages of voiced and unvoiced phonemes. The sequential nature of substitution errors was further analyzed by tallying and classifying errors as anticipatory (prepositioning), reiterative (postpositioning), or metathesis. Seven percent of the substitution errors in this study were sequential, with anticipatory errors outnumbering reiterative errors by a ratio of 6 to 1. Feature analysis of substitutions to determine distance from the target sound revealed that 38% of the substitutions were defective in two or more features. Some of these subjectively bore little resemblance to the target sound.