The development of the category-recall relationship in the sorting-recall task

The relationship between categorical organization and recall for children in grades two, four, and six (ages 8, 10 and 12 years, respectively), and for adults was investigated using the sorting-recall procedure. Subjects sorted unrelated words on individual cards into either two, four, or six categories prior to output, and recall performance improved significantly as a function of increased numbers of sorting categories. The category-recall relationship was shown to be independent of the effects of subject-determined item exposure time in sorting. This result was taken as evidence for a basic structural property of memory (“chunking”) that does not vary as a function of age. We further speculated that the slopes of the category-recall function obtained in this study suggest a limit on the size of organizational units in young children's memory.     

Signal-controlled responding

Pigeons' key pecks were reinforced with grain, then extinguished. An 8-second tone preceded the availability of peck-dependent grain 1 second after tone offset. When a tone signalled grain and an 8-second clicking sound did not, three pigeons pecked during a high percentage of tone periods, but they pecked during a low percentage of click periods. When the roles of the tone and clicking sound were reversed, performance reversed. For other birds, when a key peck during the tone cancelled the availability of grain (omission procedure), the tendency to key peck during the tone decreased some, but still remained high. A third group of pigeons received the omission procedure with the addition that the tone could not end unless 2 seconds had elapsed without a key peck. The pigeons continued to respond in a high percentage of tone periods. The experiments favor an explanation based on the pairing of the tone with a reinforced response, such as Pavlovian conditioning.     

Control by stimulus features during fading.

Sixteen children were given four successive circle-size discrimination problems with luminance as the fading stimulus. Children who were first presented with a difficult size discrimination failed to acquire this discrimination. Those who first received an easy discrimination learned the difficult discrimination. At the end of each 10-trial block, two probe stimuli were presented to monitor any shift in control from luminance to size. One probe was the same size as the positive stimulus but of different luminance; the other was the same luminance but of different size. If, in the course of fading, size and luminance both controlled responding, fading was successful. If luminance alone controlled responding until the end of fading, the size discrimination was not established. Dual control, and thus successful fading, resulted when the target stimuli were very discriminable, or when the target stimuli were subtly different provided that previous fading series had first established less subtle discriminations.     

Autoshaping with common and distinctive stimulus elements, compact and dispersed arrays

Four groups of pigeons were trained with a standard autoshaping procedure in which a brief fixed-duration interval always followed by a grain delivery alternated with a longer variable-duration interval never associated with grain delivery. One of two stimuli was always presented during each interval. One of them contained three black dots and a black star on a green background; the other contained four black dots on a green background. The four elements of each stimulus were arranged in a more compact array for two groups and in a more dispersed array for the other two groups. Which of the two stimuli preceded grain delivery was counterbalanced within each pair of groups. The speed of occurrence of the first autoshaped peck was not affected by whether the stimulus containing the distinctive star element preceded grain delivery, but autoshaping was faster when the stimulus arrays were compact than when they were dispersed. During 560 response-independent training trials that followed the first autoshaped peck, this pattern reversed; both discriminative control over responding and the relative frequency of pecking the stimulus that preceded grain delivery were greater for the two groups where this stimulus contained the discriminative element than for the two groups where it contained only common elements. During subsequent testing with stimuli containing only a single element each, the distinctive feature was responded to proportionately more often by the two groups for which it had been an element of the stimulus preceding grain delivery than by the two groups for which it had been an element of the stimulus complex that never was associated with grain delivery. These data add further support to the hypothesis that the initial occurrence of autoshaped responding and its subsequent maintenance are not affected by the same variables. They also suggest that automaintenance is as sensitive as response-dependent training to the presence or absence of a distinctive stimulus element among several common elements and that this sensitivity appears to be independent of the specific method used for presenting the stimuli during automaintenance.     

Cumulative integrated electromyographic activity of selected speech-related muscle groups of nonstutterers during massed oral readings

The electromyographic (EMG) integrated amplitude of masseter and laryngeal muscle groups were analyzed during five massed oral readings of 16 nonstuttering adult subjects. Reduction in dysfluencies were observed over the five trials as was a reduction in reading time across trials. Significant decreases in EMG activity across trials were found for the laryngeal, but not the masseter, EMG activity. This suggests that changes in vocal behavior thought to accompany adaptation are reflected in decreases in EMG activity of select speech-related muscle groups.     

Duration of subsegments within the intervocalic interval in stutterers and nonstutterers

Intervocalic intervals (IVI) from the contextual fluent speech of 14 stutterers and controls were examined at one-quarter speed on simultaneously prepared spectrograms and intensity x time displays. Seven subsegments within the IVI were identified and their durations compared between the two groups. Stutterers were slower than controls in transitional subsegments, corresponding to movements of the tongue and larynx, but not in steady-state subsegments. The results are interpreted as suggesting that stutterers are not able to move their laryngeal and supralaryngeal structures as quickly as nonstutterers.     

Some correlates of stuttering severity judgments

Thirteen adult male stutterers recorded the Amplifier Passage on high-quality audiotape. One sentence from each recording was paired with one sentence from each of the remaining 12 recordings. The resulting 78 sentence pairs were presented to eight speech-language pathologists who were asked to judge which stutterer in each pair was more severe and to rate the confidence of each of these judgements. The confidence ratings were analyzed by means of the individual differences model of multidimensional scaling. The results suggested that reading rate and the number of intrasentence pauses were important parameters in determining the severity of stuttering.     

A critical review of a recent decade of stuttering research

The purpose of the present investigation was to catalogue and evaluate portions of the literature on stuttering from 1967 to 1977. Of particular interest was the identification of the research literature. Of 287 articles located and evaluated, 181 were research reports. These reports were categorized according to topics, subject selection, subjects' characteristics, type of research designs and use of randomization, reliability, and statistical methods. Unhappily, many of the faults identified in reviews ten to twenty years earlier tended to persist, and many of the deficiencies recently cited by authorities in the field were found to characterize this literature.     

An alaryngeal stutterer: A case history

This case study describes an individual who as a stutterer underwent a total laryngectomy and right hemithyroidectomy. Following the Doehler method of esophageal voice training, the client continued to exhibit dysfluent speech behaviors. The Iowa “Stutterer's Self-Rating of Reactions to Speech Situations” and the “Checklist of Stuttering Behaviors” were used to ascertain whether the stuttering behaviors had changed and to what degree.     

An acoustical analysis of stutterer''s speech prior to and at the termination of speech therapy

The speech of nine adult stutterers was analyzed acoustically prior to and at the termination of a modified Van Riperian procedure to determine if therapy produced discernable changes in their post-therapy fluent speech. The findings indicate that stuttering frequency decreased significantly and reading rate decreased by a statistically insignificant amount during the course of therapy. Vowel duration and the occurrence of voicing during the stop consonant production increased significantly. These findings support the hypothesis that stuttering therapy can affect more than the fluency and rate characteristics of the stutterer's posttherapy speech.