Hefting for a maximum distance throw: a smart perceptual mechanism

Objects for throwing to a maximum distance were selected by hefting objects varying in size and weight. Preferred weights increased with size reproducing size-weight illusion scaling between weight and volume. In maximum distance throws, preferred objects were thrown the farthest. Throwing was related to hefting as a smart perceptual mechanism. Two strategies for conveying high kinetic energy to projectiles were investigated by studying the kinematics of hefting light, preferred, and heavy objects. Changes in tendon lengths occurring when objects of varying size were grasped corresponded to changes in stiffness at the wrist. Hefting with preferred objects produced an invariant phase between the wrist and elbow. This result corresponded to an optimal relation at peak kinetic energy for the hefting. A paradigm for the study of perceptual properties was compared to size-weight illusion methodology.     

Kinematic form and scaling: further investigations on the visual perception of lifted weight

Observers are able to judge accurately the weight lifted by another person when only the motions of reflective patches attached to the lifter's major limb joints and head can be seen (Runeson & Frykholm, 1981). What properties of these complex kinematic patterns allow judgments of weight to be made? The pattern of variation in velocity of the lifted object over position is explored as a source of information for weight: It is found to provide limited information. How are variations in kinematic patterns scaled to allow judgments of weight, a kinetic quantity? The possibility of a source of information for scaling in the kinematics is investigated. Judgments based only on patch-light displays are accurate to a degree that is improved by an extrinsic scaling basis. Finally, the sensitivity to scaling of alternative metrics used in judging is explored. Intrinsic metrics are discovered to be less sensitive to the absence of an extrinsic basis for scaling.     

Correlates of age at first sexual intercourse in a national sample of young women

A subsample of 814 sexually experienced adolescent females from the 1979 U.S. National Survey of Young Women was analyzed to assess the correlates of age at 1st sexual intercourse. Multiple regression procedures were used to examine sets of variables sequentially. In the hierarchical regression model, the control variables (respondent's age, race, religion, and age at menarche), along with 3 independent variables (household income, ideal age at 1st marriage, and ideal age for 1st birth), predicted age at 1st intercourse. The control variables accounted for a major portion of the variance in the model. Of the controls, chronological age and age at menarche were highly significant across all models tested.     

Accreditation Standards for University and College Counseling Centers

The accreditation standards outlined in the article are used by the International Association of Counseling Services, Inc., as the basis for the formal accreditation of college and university counseling programs throughout the United States and Canada. They reflect the program elements and practice standards that are deemed essential in a counseling center that provides high-quality services to students.     

Task dynamics and resource dynamics in the assembly of a coordinated rhythmic activity.

Task dynamics corresponding to rhythmic movements emerge from interactions among dynamical resources composed of the musculature, the link segments, and the nervous and circulatory systems. This article investigated whether perturbations of interlimb coordination might be effect over circulatory and nervous elements. Stiffness of wrist-pendulums oscillated at a common tempo and at 180 degrees relative phase was perturbed through the use of tonic activity about an ankle. Left and right stiffnesses, the common period, and the phase relation all changed. Stiffnesses increased with ankle torque in proportion to the wrist's inertial load. Despite different changes in stiffness at the two wrists, isochrony was preserved. The stability was shown to be consistent with the proportionality of changes in stiffness to the inertial loads. The phase departed from antiphase in proportion to the asymmetry of inertial loads. The size of departures decreased with increasing ankle torque. An account was developed in terms of muscular, circulatory, and nervous functions.     

Visual perception of mean relative phase and phase variability

Perception of relative phase and phase variability may play a fundamental role in interlimb coordination. This study was designed to investigate the perception of relative phase and of phase variability and the stability of perception in each case. Observers judged the relative phasing of two circles rhythmically moving on a computer display. The circles moved from side to side, simulating movement in the frontoparallel plane, or increased and decreased in size, simulating movement in depth. Under each viewing condition, participants observed the same displays but were to judge either mean relative phase or phase variability. Phase variability interfered with the mean-relative-phase judgments, in particular when the mean relative phase was 0 degrees. Judgments of phase variability varied as a function of mean relative phase. Furthermore, the stability of the judgments followed an asymmetric inverted U-shaped relation with mean relative phase, as predicted by the Haken-Kelso-Bunz model.     

Distortions in definite distance and shape perception as measured by reaching without and with haptic feedback

Psychophysical studies reveal distortions in perception of distance and shape. Are reaches calibrated to eliminate distortions? Participants reached to the front, side, or back of a target sphere. In Experiment 1, feedforward reaches yielded distortion and outward drift. In Experiment 2, haptic feedback corrected distortions and instability. In Experiment 3, feedforward reaches with only haptic experience of targets replicated the shape distortions but drifted inward. This showed that outward drift in Experiment 1 was visually driven. In Experiment 4, visually guided reaches were accurate when participants used binocular vision but when they used monocular vision, reaches were distorted. Haptic feedback corrected inaccuracy and instability of distance but did not correct monocular shape distortions. Dynamic binocular vision is representative and accurate and merits further study.     

Parental ratings of son's behavior problems in high-risk families: convergent validity,internal structure,and interparent agreement

In this research, we examined the convergent validity, internal structure, and interparent agreement of the Child Behavior Checklist (CBCL; Achenbach, 1991a) using data from a community sample of 317 high-risk families. The sample consisted of 218 families with alcoholism (biological mother, father, and son) and 99 matched comparison families without alcoholism; all families were intact and included a 3- to 5-year-old son at first contact. Evidence was found for the convergent validity of the CBCL. In addition, although interparent agreement was low, the internal structure was confirmed, and structural invariance was high between mothers and fathers and in families with and without alcoholism. The effects of parental psychological and cognitive functioning on parent agreement were examined and found to have a minimal effect on parent agreement. These results demonstrate the validity of the CBCL for use by parent raters with alcoholism and their sons and emphasize the importance of including both versus only 1 parent in research using the CBCL.