Form and exploration of mechanical stability limits in erect stance

The stability limits of erect stance are described as a geometrical structure in a movement space. Mechanical properties and response latency, a neural property, are determining factors for the stability limits. Standing stability limits of adults and young children are compared, and a simple scheme is suggested by means of which infants can discover the stability limits as they learn to stand. The mechanics of different standing movements are discussed because their spatial temporal properties relate directly to their different stability limits. The combination of the stability limits for different movements gives a total set of stability limits, a different structure for adults than for children.     

On task and theory specificity

One of the significant limitations of the motor control and skill acquisition domain is that the theories, models, and hypotheses are, in most cases, task specific. Many lines of theorizing fail to hold up under even small changes in task constraints, although clearly the field does have some robust phenomena. It is proposed that a broader consideration of the role of task constraints, which is grounded in the methodology of nonlinear dynamics, may help to formulate a more general action theory of coordination and control.     

Skill, strength, handedness, and fatigue

Thirty male subjects, 20 of whom were self-classified left-handers and 10 right-handers, were tested on a grip-strength task and a handwriting task with each hand, both under normal conditions and in a situation of induced experimental fatigue. On the basis of questionnaire scores, the left-handers were sub-divided into two groups comprising the 10 most left-handed and the 10 least left-handed subjects. The test of grip strength showed a small but significant deterioration in performance of both hands from fatigue. With the handwriting task, a similar significantly adverse effect of fatigue was recorded for all groups as well as a large significant difference in performance between the preferred and nonpreferred hands under normal conditions, which decreased under fatigue. An explanation of these differential effects is discussed in terms of the greater efficiency of the preferred hand in the highly developed skill of handwriting.     

Cheating following success and failure in heavy and moderate social drinkers

Two groups of American undergraduates (moderate and heavy social drinkers) completed a matrix task and received either positive or negative feedback on their performance. Following this they were given a maze task, which was designed so that cheating could be detected. Heavy drinkers cheated more than moderate drinkers under success conditions (positive feedback). Heavy drinkers who received positive feedback also cheated more than heavy drinkers who received negative feedback. The results are interpreted in terms of self-handicapping theory.     

Effects of coping skills training on generalized self-efficacy and locus of control

A number of studies have shown that mastery experiences strengthen self-efficacy expectancies that are specific to the mastery situation. In this study I assessed the effects of cognitive-behavioral coping skills training on generalized expectancies concerning self-efficacy and locus of control in test-anxious college students. Compared with a waiting-list control group, the trained subjects exhibited significant decreases on trait and state measures of test anxiety and a higher level of academic performance on classroom tests, as well as changes in specific self-efficacy expectancies relating to test-anxiety management and academic performance. Consistent with generalization predictions derived from self-efficacy theory, the coping skills group also exhibited decreases in general trait anxiety and increased scores on a trait measure of generalized self-efficacy. Locus of control was unaffected by the program, and changes in general self-efficacy were unrelated to changes in locus of control, suggesting the possibility that different parameters of experience are related to changes in the two types of generalized expectancies.     

THE USE OF BEHAVIORAL ASSESSMENT TO PRESCRIBE AND EVALUATE TREATMENTS FOR SEVERELY HANDICAPPED CHILDREN

Behavioral assessment procedures were used to prescribe and evaluate treatments of maladaptive behavior for 2 children with severe multiple handicaps. In Experiment 1, the results of an assessment of reinforcer preference were used in conjunction with a functional analysis of the conditions maintaining self-injurious behavior to prescribe a treatment for a child with severe disabilities. The treatment procedure involved the use of a pressure-sensitive microswitch to activate reinforcing stimuli during two solitary conditions, during which self-injurious behavior had occurred at high rates. The results were evaluated with a multiple baseline across settings design and indicated that self-injury decreased with concomitant increases in microswitch activation. Results were maintained at 6 weeks, 8 weeks, and 6 months. In Experiment 2, the results of behavioral assessments of reinforcer preference and self-injurious behavior were combined to develop a treatment for a second severely handicapped child, who exhibited high rates of self-injury in demand situations. This treatment was evaluated with a multiple baseline across tasks design and resulted in the elimination of self-injury for up to 15 months.     

EVALUATION OF TACTILE PROMPTS WITH A STUDENT WHO IS DEAF,BLIND, AND MENTALLY RETARDED

We provided tactile cues to a student who was deaf, blind, and mentally retarded to guide her performance on a variety of packaging tasks. The student had previously received extensive training on multiple packaging and sequencing tasks through her vocational education program. Although she was able to complete these tasks, each change in materials necessitated that similar levels of retraining be conducted in order for her to perform revised tasks. Tactile cues were introduced and evaluated through a multiple baseline with sequential withdrawal design for two envelope-stuffing tasks and one bagging task. Results indicated that the tactile prompts were effective in guiding her performance on the training task and in promoting generalization to novel tasks and cues. Continued use of the cues was necessary to maintain the student's performance. Our findings suggest that tactile prompts function similarly to picture prompts and may be an effective alternative external prompting system for persons for whom picture prompts would not be appropriate.     

Eyewitness accuracy and confidence: within- versus between-subjects correlations

Previous researchers using between-subjects comparisons have found eyewitness confidence and accuracy to be only negligibly correlated. In this study, we examined the predictive power of confidence in within-subject terms. Ninety-six subjects answered, and made confidence ratings for, a series of questions about a crime they witnessed. The average between-subjects and within-subject accuracy-confidence correlations were comparably low: r = .14 (p less than .001) and r = .17 (p less than .001), respectively. Confidence is neither a useful predictor of the accuracy of a particular witness nor of the accuracy of particular statements made by the same witness. Another possible predictor of accuracy, response latency, correlated only negligibly with accuracy (r = -.09 within subjects), but more strongly with confidence (r = -.27 within subjects). This pattern was obtained for both between-subjects and within-subject comparisons. The theoretical and practical implications of these results are discussed.