Child performance on discrimination tasks: Effects of amount of stimulus variation

Two independently conducted studies investigated stimulus variation effects on children's discrimination learning. The stimuli in the first study were generated by a conjunctive rule and were presented in pairs. Mean trials to criterion was significantly lower for the single-feature change treatment (17.4) than for the multiple-feature change treatment (29.9). Single-feature change-treatment transfer scores were significantly higher only for stimuli that differed in terms of one of the features. The second study not only replicated the initial finding concerning the single-feature change treatment but also found that students made more errors in reaching criterion when stimuli were generated by an exclusive disjunctive rule and were presented singly. For all tasks, the single-feature change treatment with stimuli presented in pairs was accompanied by fewer errors to criterion than the other treatments.     

Differences in the search rate of children and adults in short-term memory

When people recognize a test item as belonging or not belonging to a previously presented set, recognition latency increases with the number of items in the set. Although some evidence suggests otherwise, it is currently held that the rate of this increase is the same for children and adults. In contrast, the present experiments indicated a much slower search rate for second graders (mean age = 7.33 years) than for seventh (mean age = 12.50 years) and twelfth graders (mean age = 17.25 years). Moreover, search rate for second graders was invariant under instructions which did or did not emphasize speed and with presentation of the memory set in either the auditory or visual modality. Experiment II showed that the slow search rate for children was not due to differences in encoding between children and adults.     

Effects of false increasing,decreasing, and true electromyographic biofeedback on the frequency of stuttering

Adult stutterers received auditory feedback of laryngeal area muscle activity while reading aloud under three conditions: (1) False Increasing Feedback, (2) False Decreasing Feedback, and (3) True Feedback. The subjects were unaware that the feedback in two conditions was being altered and were instructed not to manipulate the feedback signal. Decreases in the frequency of stuttering were observed for both the false increase and true feedback conditions. Factors contributing to the effectiveness of biofeedback techniques with stutterers are discussed.     

Stage 2 processing and the divided-attention effect

In two experiments subjects performed a choice-reaction-time (CRT) task and a second task concurrently. The second task was a simple reaction-time task in Experiment 1 and sentence generation and recall tasks in Experiment 2. Both studies yielded two main findings: Performance of the second task was not affected by CRT memory load (one, two, or four items), and the requirement to perform the second task did not affect the rate of increase of CRT with memory load. The first finding indicates that the effect of memory load on CRT is attributable to memory scanning, or Stage 2 processing, and is not an artifact of the rehearsal demands of the CRT memory set. The second finding indicates that Stage 2 processing is not sensitive to division of attention between the CRT and a second task.     

Modification of impulsive tempo in learning-disabled pupils

Thirty-three impulsive learning- disabled males, aged 9–12 years, were assigned to one of three treatment conditions: (a) Modeling, in which subjects were exposed to a videotape of a boy demonstrating reflective problem-solving activities and instructing himself to perform cautiously; (b) Modeling Plus Self-Verbalization, in which subjects observed the same videotape and were additionally required to verbalize similar reflective instructions; and (c) Control, in which subjects were shown a videotape of the task materials used in the modeling videotape, but without the model. Subjects were tested immediately after exposure to treatment, and again 3 weeks later, on different forms of the Matching Familiar Figures test. Both Modeling and Modeling Plus Self-Verbalization conditions were superior to Control in reducing errors on the immediate test, but the three treatments did not differ on the delayed test. No significant differences among the three conditions were found with regard to response latency. Discrepancies between the present results and those of previous related studies were noted, and potential research directions were suggested.The authors appreciate the cooperation and support of Mr. Dan Hurd, superintendent of DeKalb County Special Education Association.     

What do you do after you say hello? Observing,coding, and analyzing parent-infant interactions

Procedures for observing, coding, and analyzing parent-infant interactions are described. Sample data are presented to illustrate the outcome of these procedures and the manner in which developmental issues can be addressed using the hardware and software systems described.     

Adaptation to delayed auditory feedback

Delayed auditory feedback disrupts the production of speech, causing an increase in speech duration as well as many articulatory errors. To determine whether prolonged exposure to delayed auditory feedback IDAFI leads to adaptive compensations in speech production, 10 subjects were exposed in separate experimental sessions to both incremental and constantdelay exposure conditions. Significant adaptation occurred for syntactically structured stimuli in the form of increased speaking rates. After DAF was removed, aftereffects were apparent for all stimulus types in terms of increased speech rates. A carry-over effect from the first to the second experimental session was evident as long as 29 days after the first session. The use of strategies to overcome DAF and the differences between adaptation to DAF and adaptation to visual rearrangement are discussed.     

Effect of sample presentation time on long-delay matching in the pigeon

The effect of sample stimulus presentation time on long-delay matching in highly practiced pigeons was investigated. The birds were found capable of above chance matching performance at a delay of 60 sec provided the sample stimulus was presented for 4 sec or longer. Matching accuracy increased as a negatively accelerated function of sample stimulus presentation time and decreased as a negatively accelerated function of time since the termination of the sample. The rate of forgetting was found to be independent of sample stimulus presentation time. The data were inconsistent with a temporal discrimination interpretation of the effect of presentation time on delayed matching. The data were interpreted as supporting a simple trace strength and decay model of pigeon delayed matching.