The effects of exaggerated stress and melodic intonation on auditory comprehension abilities of aphasic adults

The purpose of this study was to determine whether significant differences existed in aphasic individuals' abilities to comprehend stimuli with differing degrees of intonation and stress. The subjects included ten aphasics, each with a Z score between -.5 and + .5 on the auditory subtests of the Boston Diagnostic Aphasia Exam (Goodglass and Kaplan, 1972), elapsed time of brain trauma not less than two months, no premorbid communication impairment, hearing sensitivity at 30 dB or better in the better ear, vision and manual dexterity adequate for the task as demonstrated by the person's ability to point to one out of four pictures.

The subjects were presented thirty randomized sentences, ten of each under the following conditions: normal stress, exaggerated stress, and melodically intoned. Their task was to point to one of four pictures which best illustrated the auditory stimulus being presented. Their responses were scored as correct or incorrect.

Responses to stimuli presented with exaggerated stress provided the greatest number of correct responses of the three stimulus conditions, while the least number of correct responses occurred to stimuli which were melodically intoned. Responses to the normal stress condition were better than those of the melodically intoned condition and poorer than those of the exaggerated stress condition. To determine if a significant difference occurred among the three auditory conditions, a treatments by subjects analysis of variance was utilized. The results of this analysis indicated that there were no significant differences among the three stimulus conditions. Even though variations in stress did not significantly improve auditory comprehension abilities of the group as a whole, some improvement was noted for individual subjects for the exaggerated stress condition as compared to the other conditions.

Additional observations of the data revealed no error patterns for the group nor for individual subjects. It was discovered that the ten sentences did differ in degree of difficulty with the possessive pronouns being the most difficult across all subjects and for all three conditions. The sentences also differed in that the variations in stress did not affect the ten sentences similarly.

These results, unlike those of previous studies, showed that exaggerated stress did not improve auditory comprehension of aphasic adults. Possible explanations for the differences between results of this study and those of previous studies include the dissimilarity among the experimental tasks, the number of variables being altered in the stimulus, and the varying ranges of auditory comprehension abilities of the subjects. The dissimilarity among the tasks appears to be the most plausible explanation for the differences between the results of this study and those of previous studies. To account for the results of the present study, several explanations were offered. First, the way in which stress was altered in the present study may not have made the stimuli more salient for the aphasic subjects. Secondly, it may be that stress alone does not improve comprehension. Other explanations include deterioration of the quality of the auditory stimulus presented by a language master, the ease of the task for some subjects, and the uniqueness of the melodically intoned stimuli. Of these five explanations, the explanations which appear most likely are the way in which stress was altered and the fact that stress alone may not improve auditory comprehension abilities of aphasic adults.

In summary, the results of the present study indicate that for the sample of aphasics used in this study, there was no significant difference in auditory comprehension of sentences presented with normal stress, exaggerated stress, and melodic intonation. Therefore, it may be concluded that variations in stress, such as those utilized in this study, will not significantly alter auditory comprehension abilities of aphasic subjects who have comprehension skills similar to those of the subjects in this study. However, there may be some individuals for whom one condition significantly enhances comprehension skills.