Force variability in isometric responses

In the present study we examined the contribution of different impulse parameters to peak force variability in an isometric task. Five experiments are reported that each held constant a different impulse parameter while allowing the other impulse parameters to vary. The results indicate that change in force level is the parameter that has the greatest effect on peak force variability, although time to peak force and preload also systematically influence response variability. A formula that accommodates the relation between impulse parameters and force variability is proposed. The data suggest that even in isometric tasks, it is the force-time properties of the impulse, rather than discrete parameters such as peak force, that determine the outcome variability.     

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.     

Response timing variability: coherence of kinematic and EMG parameters

A detailed kinematic and electromyographic (EMG) analysis of single degree of freedom timing responses is reported to (a) determine the coherence of kinematic and EMG variability to the reduced timing error variability exhibited with amplitude increments within a given criterion movement time and (b) understand the temporal organization of various movement parameters in simple responses. The data reveal that the variability of kinematic (time to peak acceleration, duration of acceleration phase, time to peak deceleration) and EMG (duration of agonist burst, duration of antagonist burst, time to antagonist burst) timing parameters decreased with increments of average velocity in a manner consistent with the variable timing error. In addition, the coefficient of variation for peak acceleration, peak deceleration, and integrated EMG of the agonist burst followed the same trend. Increasing average movement velocity also led to decreases in premotor and motor reaction times. Overall, the findings suggest a strong coherence between the variability of response outcome, kinematic, and EMG parameters.     

Group differences in intelligence and speed of information-processing

Three samples of different levels of mental ability, but each of average or above- average intelligence, were administered a battery of reaction time test which measure the speed with which persons can execute various elementary cognitive processes. Discriminant analyses revealed significant differences between the groups in reaction times and intraindividual standard deviations, and univariate analyses indicated that higher ability groups tended to obtain significantly faster mean reaction times and to show significantly less intraindividual variability than lower ability groups. Groups which differed the most in mental ability differed to the greatest extent on the more complex reaction time tests but this pattern was reversed for groups which were relatively close in mean IQ. Generally, the results support the hypothesis that speed- of-processing is an important factor unferlying intelligence, but a number of puzzling findings indicate the need for continued research in this area.     

Attentional strategies and the visual control of discrete movements

The relationship between the availability of visual information and attention demands during the production of a discrete motor act was examined. Subjects were required to move a linear slide a distance of 15 cm in both 150 and 600 msec conditions under three light manipulations, viz., light always on; light always terminated as movement began; or, subject was unsure as to whether light would stay on or terminate. A simple key press by the index finger of the opposite hand to a tone was used as a secondary task and a measure of attention demands. The light manipulation influenced attention demands on the rapid 150 msec movement such that more attention was demanded when the subject knew the light would terminate. No such attentional strategy differences were found with the slow 600 msec movement. These findings suggest that task constraints in the form of kinematic criteria, together with the perceived availability of visual information, contribute to determining attentional strategy in movement production.     

Attitude and personality characteristics of older stutterers

Attitude and personality characteristics of 29 stutterers (19 male, 10 female) aged 52–82 yr were assessed using five questionnaires. Results indicate that, while the older stutterers score approximately the same as young adult stutterers on scales assessing approach and performance behaviors, the large majority of older stutterers perceive their stuttering as less handicapping than when they were young adults. Self-perceived personality characteristics of the older stutterers were similar to a group of older nonstutterers. While a few of the subjects had experienced some degree of success as a result of treatment later in life, the majority of the subjects did not currently desire treatment.     

Perspectives on individual-family-social network interrelations

The author focuses on the trend in the family therapy field toward an expanded view of families in the context of their social environments. Within this broader eco-system perspective attention is given to individual-family-social network interrelations with implications for the family therapist.An earlier version of this paper was presented at the American Association for Marriage and Family Therapy, Dallas, Texas, October 29, 1982. Appreciation is expressed to Alice Lynn for her comments and suggestions on an earlier draft of this paper. The author has also benefitted from discussions with Douglas Sprenkle on paradigms and contexts.     

Human interventions in a behavioural experiment for Asian Elephants (Elephas maximus)

Animal Cognition - Experiments are widely used to investigate the behaviour and cognition of animals. While the automation of experiments to avoid potential experimenter bias is sometimes possible,...     

Gender roles,computer attitudes,and dyadic computer interaction performance in college students

Females tend to score lower than males on measures of computer aptitude and attitudes. This study examined the potential effects of several mediating factors, sex of experimenter, sex of experimental partner, sex typing (Bem Sex Role Inventory score), and level of past experience, on a computer interaction task involving a dyad. College students, drawn from a primarily white college population, after completing paper-and-pencil measures assessing computer experience, computer attitudes, and gender roles, participated in a computer task involving drawing up to ten prescribed geometric patterns on a computer screen. Research assistants recorded the number of correctly completed patterns and videotaped participant interaction through a one-way mirror. Males reported experiencing more computer involvement than females. For males, past computer experience and masculinity were correlated with more positive computer attitude scores. For females, only past computer experience related to more positive computer attitude scores. Analyses of the computer interaction variable indicated that participants asked male research assistants significantly more questions than female research assistants. Several interaction effects were also found.A previous version of this paper was presented at the annual meeting of the Southwestern Psychological Association, New Orleans, April 1991.