Changes in pinch force with bidirectional load forces

The forces used to grasp an object were measured while positive (push) and negative (pull) load forces were applied to the hand under varying frictional conditions. Subjects held between the tips of their thumb and index finger a manipulandum composed of two symmetrically mounted disks. The manipulandum was connected to the stage of an electromagnetic linear motor that generated load forces under computer control. In the first experiment, subjects held the position of the manipulandum constant while the motor generated forces in first the positive and then the negative direction. The motor force at which the manipulandum slipped from the fingers was measured in the second experiment. In both experiments, friction was varied by changing the surface (sandpaper, suede, or plastic) of the manipulandum disks. The pinch forces produced by subjects were linearly related to changes in motor force in both the positive and negative directions, with the slope of this relation varying as a function of the surface properties of the manipulandum. The modulation of pinch force with motor force was influenced, however, by the direction of the load force; higher forces were produced in response to negative load forces. Slip forces varied as a function of pinch force and surface texture; higher forces were associated with materials with lower coefficients of friction. These findings suggest that the friction between the skin and an object being grasped changes as a function of the direction of force that the object applies to the skin, possibly due to the anisotropic nature of glabrous skin, and that this mechanical property contributes to variations in pinch force.     

Differential thresholds for limb movement measured using adaptive techniques

Differential thresholds for limb movement were measured in 10 subjects, using the transformed up-down procedure. Subjects were required to indicate which of two random displacement perturbations delivered to their forearms had the larger standard deviation (SD). TheSD of the reference signal was fixed for each experimental condition at one of seven values ranging from 0.05 to 3.2 mm. TheSD of the other signal varied depending on the subject’s response. Using this procedure, the differential threshold for limb movement was calculated to be 8%, which is very similar to the thresholds estimated previously for changes in limb position (9%) and force (7%). The sensitivity of the human proprioceptive system to changes in limb displacement was much greater than anticipated, with subjects being able to resolve a 5-μm difference between two perturbations delivered to their arms.     

UNDERSTANDING,JUSTIFICATION AND THE A PRIORI

Philosophical Studies -     

Cuing efficiency in a Stroop-like task with visual half-field presentation

Stroop-like stimuli were presented to either the left or the right visual half-field. Subjects responded to the identity of the words above and below (the target dimension), which appeared above or below a reference point (the cuing dimension). Automatic Stroop-like effects were assessed as the difference in reaction times between congruent trials (e.g., above the reference point) and incongruent trials (e.g., above below the reference point) when both trial types were equally frequent. In blocks in which most trials were of one type (e.g., 80% congruent trials), controlled Stroop-like effects could be assessed. Automatic Stroop-like effects remained unchanged under different task manipulations. In contrast, controlled Stroop-like effects were reduced by lowering cue-response compatibility and by increasing the response alternatives from two to four. Thus, similar to other cuing effects, controlled Stroop-like effects are susceptible to manipulations that affect the response-decision stage and appear to involve response-selection processes. The resources supporting these response-selection decisions were not hemisphere-specific, and were sufficiently nonspecific that interference from a memory-load task was found. When resources were scarce, a consistent bias to attend to stimuli presented or responded to on the right was evident.     

Commitment as psychological process: Theory and pastoral implications

Persons today must devote significant effort to making and remaking personal commitments in a variety of contexts, both interpersonal and social in the larger sense. Therefore, it is important for pastors to acquire an understanding of the basic dynamics of the committing process. It is proposed that this process be viewed as a form of creativity involving four alternating phases, in which regression in the service of the ego allows deep and realistic commitments of self to be formed. Implications for pastoral care are suggested.     

The effects of dance team participation on female adolescent physical fitness and self-concept

The purpose of this study was to determine to what extent female physical fitness and self-concept are affected by dance team participation in high school. Eight dancers were tested once prior to and once four months after dance team participation. Eight participants from physical education classes, matched for age, weight, height, grade, and race, were tested once at the same time as the second dance team test. Physiological tests were maximum oxygen uptake, sit-and-reach, one-repetition maximum bench press, skinfolds, and hydrostatic weighing. The self-concept tests were Coopersmith Self-Esteem Inventory, Tennessee Self-Concept Scale, and Body Cathexis Scale. Dependent one-tailed t tests were run to determine differences between dance team pre- and posttests and control and dance team posttests. Dance subjects increased maximum oxygen uptake and one-repetition maximum bench press in addition to improving their body composition as evidenced by a significant decrease in total skinfolds and a near significant decrease in percent body fat. The dance team had a significantly higher maximum oxygen uptake than did controls. No other significant differences were seen between groups. Dance team participants significantly improved physical self and social self on the Tennessee Self-Concept Scale. No other significant differences were seen. A factor that may have affected the self-concept results in this study was low dance team status, due to a combination of unsuccessful previous dance teams and a losing football season. Within the limitations of this study, these results indicate that physical fitness is improved as a result of dance team participation; however, self-concept seems to be affected only minimally, if at all, as compared with participation in physical education classes.     

Care and the dynamics of social world

The concept of social world is formulated for the purpose of deepening our understanding of the dynamics of inclusion, exclusion, and care in interpersonal interaction. World is defined as an irreducible subject-object polarity.Social world is the extremely fragile environment within which people meet, and is easily destroyed. With special attention to family and church life, the conditions for maintaining or losing this environment are examined. Three levels of social world are defined. On the highest level, mutual care, rather than shared opinion, is seen as the factor that facilitates the preservation of social world in the face of world-threatening issues.     

Self-disclosure and liking: Effects for senders and receivers1

This experiment tested the social reward potential of self-disclosure and its impact on a receiver's attraction towards the sender. Further, a sender self-perception effect was tested. Just as a receiver is speculated to use the intimacy level of a disclosure as an indication of sender regard and trust, the self-perception hypothesis maintains that the sender also uses intimacy level to self-attribute liking and trust for the receiver. A forced-compliance procedure with college males was used to have a sender subject send either a high or low intimacy self-disclosure essay. Consistent with the social reward and self-perception hypotheses were measures of sender's behavior as trusting and measures of feelings during the disclosure process. General measures of liking and trust were not successful, however.     

Book reviews

BODEN, MARGARET A. Artificial Intelligence and Natural Man. Hassocks : Harvester Press Limited, and New York: Basic Books Inc., 1977. Pp. ix+537. £613.50 hardback; £64.95 paperback. ISBN 0 85527 435 2.

ESTES, W. K. (Ed.). Handbook of Learning and Cognitive Processes. Vol. 6. Linguistics. Functions in Cognitive Theory. Hillsdale, N.J. : Erlbaum Associates. 1979. Pp. 331. £12.70. ISBN o 470 26311 3.

O'KEEFE, J. and NADEL, L. The Hippocampus as a Cognitive Map. London: Oxford University Press. 1978. Pp. 543. £25.00. ISBN 0 12 524150 X.

FITZSIMONS, J. T. The Physiology of Thirst and Sodium Appetite. Cambridge: Cambridge University Press. 1979. Pp. 572. £32.50. ISBN 0 521 22292 3.

MURRAY, F. B. and PIKULSKI, J. J. (Eds). The Acquisition of Reading. Baltimore: University Park Press. 1978. Pp. 178. £8.95. ISBN 0 8391 1281 5.

NEWTON, M. J., THOMAS, M. E. and RICHARDS, I. L. Readings in Dyslexia. Wisbech: Benrose Ltd. 1979. Pp. 203. £4.50. ISBN 09 0511 4124.

SENDERS, J. W., FISHER, D. F. and MONTY, R. A. (Eds). Eye Movements and Higher Psychological Processes. Hillsdale, N. J. : Erlbaum. 1978. Pp. 394. £19.95. ISBN 0 470 26489 6.

GRUBER, H. E. and VONECHE, J. J. (Eds). The Essential Piaget. London: Routledge & Kegan Paul. 1977. Pp. 880. £12.95. ISBN 07100 87780.

SIEGEL, L. S. and BRAINERD, C. J. (Eds). Alternatives to Piaget. New York: Academic Press. 1978. Pp. 262. £11.70. ISBN 12 641950 7.

BRANSFORD, J. D. Human Cognition: Learning, Understanding and Remembering. Belmont, California: Wadsworth. 1979. Pp. xii+300. £11.85. ISBN 0 534 00699 X.

VON FIEANDT, K. and MOUSTGAARD, I. K. The Perceptual World. London: Academic Press. 1977. Pp. 680. £32.00. ISBN 0 12 725050 6.

BURTON, A. and RADFORD, J. (Ed.). Thinking in Perspective: Critical Essays in the Study of Thought Processes. London: Methuen. 1978. Pp. xxii+232. £3.95. ISBN 0 416 85840 6.

MAYER, R. E. Thinking and Problem Solving: An Introduction to Human Cognition and Leavning. Glenview, Illinois: Scott, Foresman and Company. 1977. Pp. viii+214. £4.95. ISBN 0 673 15055 0.

BATES, E. Language and Context: The Acquisition of Pragmatics. New York: Academic Press. 1976. Pp. 375. £14.50. ISBN 0 12 081550 8.

MILGHAM, N. W., KRAMES, L. and ALLOWAY, T. M. Food Aversion Learning. New York: Plenum Press. 1977. Pp. 263. £27. ISBN 0 306 31040 6.

O'CONNOR, N. and HERMELIN, B. Seeing and Hearing and Space and Time. London: Academic. 1978. Pp. 157+viii. £6.80. ISBN 0 12 524150 X.     

Book reviews

GEOGRAPHY, R. L. and GOMBRICH, E. H. (Eds). Illusion in Nature and Art. Gerald Duckworth and Co Ltd. 1973. Pp. 288. £7.50/£3.25.

HARTMANN, E. L. The Functions of Sleep. London: Yale University Press. 1974. Pp. 198. £ 3.50.

RADFORD, J. and BURNTON, A. Thinking: its Nture and Devolopment. London: Wiley. 1974. Pp. 440. £ 6.95. Soft cover £ 3.25.

MACE, C. A. Selected Paper. London: Methuen and Co Ltd. 1973. Pp. 420. £ 6.50.

WOLFF, J. G. Language, Brain and Hearing. London: Methuen and Co. Ltd. 1973 Pp. 237. £ 3050.

BATTRO, A. M. Piaget: Dictionary of Terms. Oxford: Pergamon Press Ltd. 1973. Pp. 186. £ 5.75.

MUSSEN, P. H. and ROZENSWEIG, M. R. Annual Review of Psychology. Annual Reviews Inc: Palo Alto, Califonia. Pp. 551. 12.50.