The Organization of Multisegmental Pulls Made by Standing Humans: II. Submaximal Pulls

Previously, an autonomous oscillator model with three parameters was derived that describes the relationship between anterior-posterior center of mass motions and pulling force for near-maximal, bimanual pulls made by standing subjects (Michaels, Lee, Pai, 1993). The present study evaluated the extent to which a full range of pulling forces could be fit by the model and how the model's three parameters changed with intended pulling force. How much variation in force each parameter could contribute was determined by simulating the model. Qualitative and quantitative analyses of pulls made by 6 well-practiced subjects at 5prcent;, 10prcent;, 20prcent;, 40prcent;, 60prcent;, 80prcent;, and 95prcent; of their maximum pulling force revealed that the model holds well, except for the least forceful pulls of some subjects. Two parameters appeared to be controlled; one, related to the position of the center of pressure, varied most among less forceful pulls; the second, related to the position of the center of mass at the time of handle-force onset, varied most among more forceful pulls. How these parameters might be set is discussed.     

Family characteristics of children who self-select into a prevention program for children of alcoholics

Evaluated the efficacy of a self-selection recruitment process designed to attract fourth-, fifth-, and sixth-grade children into a school-based prevention program for children of alcoholics. Participants were 296 families comprising one child and either one or both parents. Family members' self- and collateral reports were used to assess parental problem drinking, family characteristics, and individual pathology. Analyses revealed that the recruitment process was not effective in recruiting children of alcohol-abusing parents. Furthermore, families in which children received parental consent to participate in the prevention program were indistinguishable from families whose children either showed interest without obtaining consent or showed no interest at all. Implications for recruitment strategies for future prevention programs for children of alcoholics are discussed.     

Lateral interception I: operative optical variables, attunement, and calibration

J. J. Gibson (1966, 1979) suggested that improvement in perception and action can be attributed in part to changes in which variable is attended to. Such reattunement has been demonstrated with observers making judgments in response to simulations. The present study sought attunement changes in the perception of real events and in visually guided action. In 3 experiments, adults judged the passing distance of or attempted to catch balls. Discrete measures and the predictions of a modified required velocity model (e.g., R. J. Bootsma, V. Fayt, F. T. J. M. Zaal, & M. Laurent, 1997) were used to reveal which variables were exploited. Participants differed from each other and, to some extent, changed in the optical variables used, in catching as well as judging. Nevertheless, the changes were much smaller than in previous simulation-judgment studies; calibration was also found to underlie the improvements in performance.     

Information and action in punching a falling ball

Lee, Young, Reddish, Lough, and Clayton (1983) reported that the timing control of jumping and vertically punching a dropping ball exploits the inverse of the rate of change of optical expansion, τ(r). We raise a number of methodological and logical criticisms against their experiment and conclusions and attempt to rectify them by examining elbow joint angles only,in seated punchers, under both monocular and binocular conditions, with two ball sizes, dropped from two heights. Differences between the binocular and monocular cases suggest the exploitation of different information. We present several techniques to help determine the operative variable(s) controlling the action. The optical variable used to initiate and guide flexion appeared to be expansion velocity (looming), rather than τ(r); extension appeared to be under the control of different variables in the monocular and binocular cases. Simulations using single variables and single perceptuo-motor intervals were of mixed success.     

S-R compatibilities depend on eccentricity of responding hand

Bauer and Miller (1982) demonstrated that when responding on the body midline with the right hand, subjects react faster when the pairing between horizontally oriented stimuli (an X to the left or right of fixation) and vertically oriented responses (an up or down finger movement) is left-down, right-up (“anti-clockwise”) but when responding with the left hand, the converse pairing was faster. The present experiments tested whether those preferences held for responses other than on the body midline. Unimanual reaction times for clockwise and anti-clockwise S-R pairings were determined for both hands at the midline and 30 and 60 cm to the left or right. Hand position determined both the direction and extent of the compatibility preference; at eccentric positions the right hand preferred clockwise pairings and the left anticlockwise, the converse of that found by Bauer and Miller. The results extend Bauer and Miller's finding, raise problems for theories of S-R compatibility, and further reveal that the state of the action system “sets up” perception.     

Considerations Regarding Online Methods for Suicide‐Related Research and Suicide Risk Assessment

Frequent advances in technology provide new and exciting opportunities for conducting suicide research and suicide risk assessments. However, to the authors' knowledge, best practices for using technology, specifically the Internet, to conduct research protocols involving suicide risk assessments have not been examined. In research contexts, the use of technology for research on suicidal behavior and suicide risk assessment can offer benefits relative to other forms of data collection. These advantages, which include increased validity, feasibility, and efficiency, as well as improvements in data collection and management, are presented. Considerations regarding the implementation of an online system for suicide risk assessment as well as limitations and future directions are discussed.