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.     

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.     

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.     

The effects of sound duration on newborns' head orientation

Two experiments assessed the importance of sound duration for eliciting head orientation responses from newborn infants. In Experiment 1, thirty infants turned with equal frequency toward 20-s continuous rattle sounds and 20-s trains of rattle segments. The duration of the rattle segments--14 and 100 ms (2/s), or 500 ms (1/s)--did not influence the likelihood of turning. Response latencies and durations proved quite similar for all stimuli. In Experiment 2, twenty-four infants heard continuous rattle sounds of four different durations: 1, 5, 10, and 20 s. They turned reliably to all stimulus durations; furthermore, the magnitude and temporal characteristics of head orientation responses did not differ for the four stimulus durations. These results suggest that the newborn's head orientation response may reflect a motor program that is initiated by auditory input and then executed in a similar fashion regardless of further stimulation.