THE ACQUISITION AND MAINTENANCE OF SYNTHETIC SPEECH IN NON-VOCAL CEREBRAL PALSIED INDIVIDUALS

Abstract

A recent development in the field of technical aids for the handicapped is electronic speech synthesis. Whereas this revolutionary advancement may have many benefits for persons whose speech is defective or for those individuals who have lost the use of their natural speech apparatus through physical trauma, a satisfactory analysis of language training models applicable to the instruction of the Phonic Mirror Handivoice model HC 120 had not yet been accomplished. In the present study, two non-vocal cerebral palsied subjects participated throughout a series of three experiments. It was considered important to examine intensively the performances of these selected individuals as they interacted with and learned about the various aspects of a unique form of vocal behavior. In the first experiment, a traditional paired-associates procedure, Method A, was the standard training method with which other methods were compared. Method B was essentially a paired-associates procedure that emphasized the personal histories of verbal behavior for each subject; Method C established discriminative control over vocal responses by natural features of the environment; Method D combined a paired-associates procedure with one in which the subject directly supplied supplementary verbal stimuli as part of the training procedure. The criterion for effectiveness was the number of training/testing cycles required for each S to achieve criterion (of 100% correct) on each word list. The results of these comparisons indicated that none of the three methods was any more or less effective than the traditional paired-associates procedures. Upon the completion of the second comparison (i.e., Method A and Method C), an informal retention survey was conducted. The responses from both subjects to this survey indicated poor retention for test stimuli established on early lists but increasing retention on the more recently trained lists. Experiment 2 was therefore designed to determine the replicability of this retention phenomenon both within and between the two S's, using Method A, across three different word lists. This experiment showed that when test stimuli were presented 24 hours after training, there was little or no loss of control over the appropriate word. An additional finding was that little or no retention was exhibited by either S for words which had not been retested at the 24 hour interval and whose retest intervals were 4, 5, and 6 days. A feature of the Experiment 2 survey was that the variables of time (elapsed from training to testing) and additional training were confounded. Therefore, Experiment 3, again using Method A, was conducted to separately (1)evaluate the effectiveness of a simple retraining procedure on extended retention, and (2)examine the effect of elapsed time on discriminative control over the previously established verbal responses. The results of the retraining procedure were positive. Whereas previous surveys of Experiment 2 had produced little or no evidence of retention beyond the 48 hour interval, 60% of the test stimuli in Experiment 3 discriminated their appropriate verbal responses. In contrast, the word lists which had not undergone retraining at the 24 hour interval nor had been followed by additional training of new word lists exhibited retention of either 0 or 20%. Two major outcomes of the present study were (1)the four training methods were all effective, but not differentially so, in teaching the numeric language of the HandiVoice, and (2)effective retention over a number of days could be achieved by a single retraining session. These findings offer several practical guidelines for future HandiVoice instructors to establish and maintain a new but important form of verbal behavior.