Vowel duration in stutterers participating in precision fluency shaping

The purpose of this study was to determine the extent to which stutters manipulate vowel duration to achieve fluency after participating in Precision Fluency Shaping. Nine stutterers who read an all-voiced sentence fluently before and after therapy were selected for study. Wide-band spectrograms were made of the initial phrase of the sentences, and vowel durations were computed. Results indicated that extended vowel durations were characteristic of the fluency of stutterers posttherapy. The subject that had the highest rate of disfluency after therapy also had the shortest vowel durations. Clinical implications concerning the importance of speech rate during carryover practice are made.     

Selective attention and changes in clinical state

Thirty inpatients of a psychiatric unit were given the Mini-Mult and a series of auditory selective attention tasks in order to test the hypotheses that (1) impaired attention is related to degree of pathology, and (2) improvement in clinical state leads to improved ability to selectively attend. The results showed that the relationship between the Mini-Mult and the listening tasks is significant only when the subjects had to exclude irrelevant stimuli (interference condition). The results also indicated that the relationship between clinical changes and changes in attentional performance is significant. The findings were discussed in terms of a quantitative theory of attention.     

Verb semantic structures in memory for sentences: Evidence for componential representation

This research contrasts two hypotheses concerning componential storage of meaning. The Complexity Hypothesis assumed by Fodor (The language of thought, NY: Crowell, 1975), Kintsch (The representation of meaning in memory, Hillsdale, NJ: Erlbaum, 1974), and Thorndyke (Conceptual complexity and imagery in comprehension and memory. Journal of Verbal Learning and Verbal Behavior, 1975, 14, 359–369) states that a word with many semantic components will require more processing resources, comprehension time, and long-term memory space than a word with few components, and thus will interfere more with memory for surrounding words. This memory prediction was tested against an alternative prediction based on connectivity. The Connectivity Hypothesis views verb semantic structures as frames for sentence representation and states that memory strength between two nouns in a sentence increases with the number of underlying verb subpredicates that connect the nouns. Thus, the Complexity Hypothesis predicts that a verb with many subpredicates will lead to poorer memory strength between the surrounding nouns than a verb with few subpredicates, while the Connectivity Hypothesis predicts that verbs with many subpredicates will lead to greater memory strength between nouns in cases when the additional subpredicates provide semantic connections between the nouns.In three experiments, subjects recalled subject-verb-object sentences, given subject nouns as cues. General verbs, with relatively few subpredicates, were compared with more specific verbs whose additional subpredicates either did or did not provide additional connections between the surrounding nouns. The level of recall of the object noun, given the subject noun as cue, was predicted by the relative number of connecting subpredicates in the verb, but not by the relative number of subpredicates. This finding supports the Connectivity Hypothesis over the Complexity Hypothesis. These results are interpreted in terms of a model in which the verb conveys a structured set of subpredicates that provides a connective framework for sentence memory.     

Voice onset time production and perception in apraxic subjects

This study explored the relationship between the perception and production of voice onset time (VOT) in apraxic subjects. Spectrograms of the words, “bees” and “peas” spoken by apraxic subjects were acoustically analyzed to obtain a measure of VOT. The subjects also identified the initial cognate (“b” or “p”) from synthetically generated speech spanning a voiced to voiceless time continuum. The results suggest that apraxic subjects have production as well as perceptual errors in the voicing feature but no significant relationship was found between the two measures.     

Short-term retention of response outcome as a determinant of serial reversal learning

The correlation between short-term retention of the outcome of the preceding response and overall learning proficiency was investigated for serial reversal learning. Pigeons were trained to asymptote on a serial reversal problem and then were presented a percentage reinforcement schedule where only some correct trials were rewarded. Nonrewarded correct trials were treated exactly as incorrect trials. The difference in error probability following the two types of correct trials was then used as a measure of short-term retention. When intertrial intervals (ITI) were short (6 sec), substantial differences occurred. When the ITI's were increased, the difference in accuracy declined regularly to no difference at an ITI of 60 sec. This demonstration of a short-term retention gradient, coupled with the finding that overall reversal learning was much better with the shorter ITI's, suggests that a primary mechanism of improvement in serial reversal learning is the acquisition of a conditional discrimination based on the outcome of the preceding response.