Controlling the Ground Reaction Force During Lifting

The control of the ground reaction force vector relative to the center of gravity (CoG) was examined while subjects performed a back-lifting task. Six male subjects (aged 24.0 +/- 2.5 years) repeatedly lifted a barbell. A biomechanical analysis that used a linked segment model revealed that the summed rotations of body segments during lifting yielded a specific rate of change of the angular momentum of the entire body. This equaled the external moment provided by Fsubg; relative to CoG. This implies that multisegment movements involve control of the angular momentum of the entire body through an appropriately directed Fsubg;. Thus, in dynamic tasks Fsubg; is pointed away from rather than lined up with the CoG, as is the case in static tasks.     

Assessing the stability of principal components using regression

This paper presents an analysis, based on simulation, of the stability of principal components. Stability is measured by the expectation of the absolute inner product of the sample principal component with the corresponding population component. A multiple regression model to predict stability is devised, calibrated, and tested using simulated Normal data. Results show that the model can provide useful predictions of individual principal component stability when working with correlation matrices. Further, the predictive validity of the model is tested against data simulated from three non-Normal distributions. The model predicted very well even when the data departed from normality, thus giving robustness to the proposed measure. Used in conjunction with other existing rules this measure will help the user in determining interpretability of principal components.The authors would like to thank the four anonymous reviewers and the two editors for their valuable comments. Atanu R. Sinha gratefully acknowledges the research support received from the Marketing Studies Center, AGSM, UCLA. Send requests for reprints to Atanu R. Sinha, B418 Gold Hall, 110 Westwood Plaza, Los Angeles, CA 90095.     

Decision strategies and visual-field asymmetries in same-different judgments of word meaning

The accuracy with which observers judged whether two words belonged to the same semantic category was determined from a detection-theoretic analysis ofsame-different judgments. In Experiment 1, one word was presented centrally and the other word in either the left visual field (LVF) or the right visual field (RVF); in Experiment 2, both words were presented to either the LVF or the RVF. In order to obtain receiver-operating characteristics (ROCs) of performance, observers were asked to rate their confidence that the two words belonged to the same semantic category. Two models of the decision strategy were fitted to the obtained characteristics: a differencing model, in which the decision variable was the difference between the two observations; and an optimal model, in which each observation was judged in relation to a criterion. In both experiments, the optimal model provided a better fit than the differencing model to the obtained characteristics. Maximum-likelihood estimates of both the criterion-free parameter,d′, and the area under the operating characteristic,p(A), were greater for words presented in the RVF than for those presented in the LVF.     

Chaos Theory,Philosophically Old,Scientifically New

In this article, the idea of chaos in relation to chaos theory will be explored in terms of its psychological meaning. Chaos theory has recently become a central area of scientific interest in psychology, and as a result it seems important to understand the deeper philosophical issues that surround the idea of chaos. Consequently, chaos will be explored in terms of its philosophical history through the ages, and some psychological speculations will be offered to explain both the disappearance and reemergence of such an important philosophical idea in modern science.     

Achievement motivation in relation to achievement-related recall,performance, and urine flow,a marker associated with release of vasopressin

Administration of the pituitary hormone, arginine vasopressin (AVP), enhances memory in animals and humans. Since AVP is the antidiuretic hormone, its release can be inferred from reductions in urine flow. Forty-six male adults recalled the contents of a complex story and then either were exposed to achievement arousal or were not. Significantly more of the subjects in the aroused than the nonaroused condition showed a decrease in urine flow, and the greater the decrease in urine flow among the achievement-aroused subjects, the better the recall of achievement-related story content 24 hours later. Subjects high inn Achievement, in the achievement-oriented condition, showed lower urine output at the outset of the second day and greater improvement in learning to unscramble words. Since lower urine output was also related to improvement in unscrambling words, achievement arousal may have released AVP which in turn may have facilitated achievement-related retention and performance.I am greatly indebted to Sean Connelly for assistance in carrying out this research and to Dr. Franklin Epstein of the Beth Israel Hospital, Boston, for helping me to understand how the kidney functions in producing urine.     

Gender differences in coping: A further test of socialization and role constraint theories

To further test role constraint and socialization theories of gender differences in coping, two studies were conducted to examine coping strategies in individuals occupying similar roles. The relations between coping strategy frequency and effectiveness and between coping strategy use and psychological functioning also were examined. Predominantly Caucasian female and male college students participated in the studies. Results indicated support for both socialization and role constraint theories. Effectiveness and frequency of coping strategy use were moderately correlated. Gender differences in cognitive appraisal varied with dispositional vs. situational assessment. The need for a more integrated model to explain gender differences in coping and implications for existing theories are discussed.     

Outcomes of inpatient group psychotherapy associated with dispositional and situational affiliativeness

Before and after participating in an intensive three-week program of group psychotherapy, 33 recently rehospitalized male veterans (mean age=42) completed the Symptom Check List-90R and the Profile of Mood States. Prior to this program they also completed a trait affiliativeness measure and later rated their subsequent group therapy sessions for situational affiliativeness. The outcome measures indicated medium to large effect size benefits, which consistently associated positively with both separate and joint measures of trait and situational affiliativeness. The results encourage greater clinical attention to affiliativeness, a construct central to interpersonal theories of personality.This article is based upon a dissertation submitted to the Department of Psychology, Michigan State University, in partial fulfillment of the requirements for the Ph.D. by the senior author.The authors express appreciation for the interest and cooperation of Drs. Bruce Vreeland, Larry Schwartz, Robert Munley, and Hope Conte and the patients of the Veterans Administration Medical Center, Battle Creek, Michigan.     

Telling stories: metaphors of the Human Genome Project

Scientists of the Human Genome Project tend to rely on three metaphors to describe their work, each of which implicitly tells much the same story. Whether they claim to interpret the ultimate “book,” to fix a flawed “machine,” or to map a mysterious “wilderness,” they invariably cast the researcher as one who dominates and exploits the Other. This essay, which explores the ways such a story conflicts with feminist values, proposes an alternative.