Temporal coordination of alternative and simultaneous aiming movements of constrained timing structure

Two experiments are reported addressing the preparation and initiation of movements with equal or unequal timing properties for both hands. Temporal coordination was examined in two movement tasks: one in which both hands performed the movements simultaneously (simultaneous aiming task) and one in which only one alternative of two possible movements was executed (choice aiming task). For each task a different group of subjects was used. Besides the timing relationships between both movements, the effects of preparation interval (1, 3, and 5 s), the average velocity (7, 14, 17.5, and 70 cm/s), the presence of advance information about the required velocity of the movement(s), and practice were investigated. Based on the common- and the specific-timing notions, distinct hypotheses were tested as to the effects of the variables on the temporal coordination as revealed by reaction time. A main result was that the effects of timing differences between the hands was task specific. For the choice task the data are in agreement with the common-timing notion of coordination, i. e., only one timing demand at a time can be prepared, whereas in the simultaneous task evidence was obtained for the specific-timing notion, i. e., independent preparation and initiation of different timing properties for the hands. However, it is argued that the results of the choice task probably do not reflect a general inability to prepare movements of different timing requirements for both hands, but is related to a task-specific strategy of selective preparation.     

“Subordination” and sensitivity to nonverbal cues: A study of married working women

Sex Roles - Women's superiority in decoding nonverbal cues of emotion has often been discussed as an adaptation to low status. To examine the relation of status to nonverbal sensitivity,...     

CORRECTING THE 16PF FOR FAKING: EFFECTS ON CRITERION-RELATED VALIDITY AND INDIVIDUAL HIRING DECISIONS

The effects of correcting a personality measure for faking were evaluated within an organizational context. Two possible repercussions of score correction were studied using the 16PF personality inventory: the effect on criterion-related validity and the effect on individual hiring decisions (i.e., which applicants would or would not be hired). Results indicated that correction for faking had little effect on criterion-related validity. However, depending on the selection ratio, correction of scores would have resulted in different hiring decisions than those that would have been made on the basis of uncorrected scores. Implications for organizations using personality measures for selection and recommendations regarding the use of faking corrections are discussed.     

Orienting the finger opposition space during prehension movements

Two experiments are reported that examined the act of prehension when subjects were asked to grasp with their thumb and index finger pads an elongated object resting horizontally on a surface and placed at different orientations with respect to the subject. In Experiment 1, the pad opposition preferences were determined for the six angles of orientation examined. For angles of 90 degrees (object parallel to frontal plane) or less, no rotation of the wrist (pronation) was used; for angles 110 degrees or greater, pronation was systematically employed to reorient the finger opposition space. Only one angle, 100 degrees , produced any evidence of ambiguity in how to grasp the object: Approximately 60% of these grasps involved pronation and 40% did not. Using the foregoing grasp preference data, in Experiment 2 we examined the kinematics of the wrist and elbow trajectories during prehension movements directed at an object in different orientations. Movement time, time to peak acceleration, velocity, and deceleration were measured. No kinematic differences were observed when the object orientation either required (110 degrees ) or did not require (80 degrees ) a pronation. By contrast, if the orientation was changed at the onset of the movement, such that an unpredicted pronation had to be introduced to achieve the grasp, kinematics were affected: Movement time was increased, and the time devoted to deceleration was lengthened. These data are interpreted as evidence that when natural prehension occurs, pronation can be included in the motor plan without affecting the movement kinematics. When constraints are imposed on the movement execution as a consequence of a perturbation, however, the introduction of a pronation component requires kinematic rearrangement.     

Changes in spinal reflex excitability in a countermanded timed response task

Subjects (N = 8) performed a timed response task in which they attempted to synchronize an impulsive foot-press response with the last in a series of four regularly spaced tones. In Experiment 1, the response was countermanded on one third of the trials (stop trials) by a stop signal that appeared at a predetermined delay after the third tone. No stop signal appeared on the remaining trials (go trials). All subjects showed a systematic transition from withholding the response on stop trials in which the stop signal appeared shortly after the third tone to executing the response on trials in which a single stop signal delay had been chosen so that a response would be made on about 50% of the stop trials. We elicited Hoffmann (H) reflexes from the soleus muscle on all trials to determine whether the reflexes were augmented on occasions on which a response was prepared but withheld. Mean H-reflex amplitudes on go trials and on stop trials on which the response was executed were similar and showed a marked augmentation beginning about 250 ms before response onset; mean H-reflex amplitudes on stop trials on which the response was withheld showed less pronounced augmentation. Inspection of individual H-reflex amplitudes revealed that on stop trials on which the response was withheld the reflexes could be augmented to the same extent as on trials on which the response was executed. This dissociation of H-reflex augmentation and response execution shows that H-reflex augmentation reflects a controlled response process. Ballistic response processes therefore must be limited to a brief duration.     

Crossing without vision of path gaps

Two experiments considered the behavior of subjects who cross gaps in a pathway without benefit of vision. The first experiment contrasted visually and nonvisually guided locomotion, finding a significantly greater number of refusals under nonvisual guidance but no loss of appropriate modulation of step components to the salient dimensions of the actor and layout. Different components of crossing were modified under guidance of different sensory systems; the lengths of the crossing and support spans were primarily altered under nonvisual guidance, and the distance of the support foot to the near edge of the gap was the component of preference under visual guidance. In the second experiment, subjects crossed nonvisually, using probes that varied in length and moment of inertia. The adaptability of the step components to actor and layout dimensions was unchanged, but there was no effect of these mechanical manipulations on the components of crossing identified in Experiment 1.     

Exchange delays and impulsive choice in adult humans.

Choice responding by adult humans in a discrete-trial task was examined as a function of conditions that manipulated either the delay to point delivery or the delay between points and their exchange for money. In point-delay conditions, subjects chose between an "impulsive" alternative that provided a small amount of points immediately and a "self-control" alternative that provided a larger amount of points delayed by 15, 30, or 60 s. Points were exchanged for money immediately following the session. Subjects preferred the self-control alternative. In exchange-delay conditions, subjects chose between a small amount of points exchangeable for money immediately following the session and a larger amount of points exchangeable for money after 1 day, 3 weeks, or 6 weeks. A self-control preference observed for all subjects in the 1-day exchange-delay condition reversed to exclusive impulsive preference for 4 of the 6 subjects when choice conditions involved exchange delays of 3 or 6 weeks. These results show that human choice is sensitive to the manipulation of exchange delays and that impulsive preference can be obtained with exchange delays on the order of weeks.     

Intuition and the socratic method: Two opposed ways of knowing?

Socratic method and intuition are two ways of knowing commonly thought as opposed. The author shows how both ways of knowing can be linked in an education that has philosophy as its armature.