Vector coding in slow goal-directed arm movements

It has been found that the estimate of relative target direction is consistently biased. Relative target direction refers to the direction in which a target is located relative to another location in space (e.g., a starting position in the case of goal-directed movements). In this study, we have tested two models that could underlie this biased estimate. The first proposed model is based on a distorted internal representation of locations (i.e., we perceive a target at the “wrong” location). We call this thedistorted location model. The second model is based on the idea that the derivation of target direction from spatial information about starting and target position is biased. We call this thebiased direction model. These two models lead to different predictions of the deviations that occur when the distance between the starting position and the target position is increased. Since we know from previous studies that the initial direction of slow arm movements reflects the target direction estimate, we tested the two models by analyzing the initial direction of slow arm movements. The results show that the biased direction model can account for the biases we find in the target direction estimate for various target distances, whereas the distorted location model cannot. In two additional experiments, we explored this model further. The results show that the biases depend only on the orientation of the line through starting position and target position relative to the plane through longitudinal head or body axis and starting position. We conclude that the initial part of (slow) goal-directed arm movements is planned on the basis of a (biased) target direction estimate and not on the basis of a wrong internal representation of target location. This supports the hypothesis that we code displacements of our limbs in space as a vector.     

The generality of word-association hierarchies: I. Production and recall of association responses

Ss responded to a stimuluslist in a free word association session (AS) and tried to recall their response to each stimulus in a recall session (RS). There was a significant positive correlation between commonality score (Co) in AS and number of correct reproductions in RS. All Ss tended to gain in Co, but LC (i.e., Ss of low Co in AS) more than HC (i.e., Ss of high Co in AS).     

Book reviews

Gormenzano, I., & Wasserman, E.A. (Eds.) (1992). Learning and memory: The behavioral and biological substrates. Hillsdale, NJ: Lawrence Erlbaum Associates, Inc. Pp. vii + 413. ISBN 0-8058-0888-4. £45.95 (Hbk).

Squire, L.R., Weinberger, N.M., Lynch, G., & McGaugh, J.L. (Eds.) (1991). Memory: Organization and locus of change. Oxford: Oxford University Press. Pp. 438. ISBN 0-19-506921-8. £55.00.

Quiatt, D., & Reynolds, V. (1993). Primate behaviour: Information, social knowledge, and the evolution of culture. Cambridge: Cambridge University Press. Pp. 322. ISBN 0-521-35255-X. £42.50 (Hbk).

Dawkins, M.S. (1993). Through our eyes only? the search for animal consciousness. Oxford: W.H. Freeman/Spektrum. Pp. x + 192. ISBN 0-7167-4501-1. £14.99 (Hbk).     

AMAB: Automated measurement and analysis of body motion

Technologies that measure human nonverbal behavior have existed for some time, and their use in the analysis of social behavior has become more popular following the development of sensor technologies that record full-body movement. However, a standardized methodology to efficiently represent and analyze full-body motion is absent. In this article, we present automated measurement and analysis of body motion (AMAB), a methodology for examining individual and interpersonal nonverbal behavior from the output of full-body motion tracking systems. We address the recording, screening, and normalization of the data, providing methods for standardizing the data across recording condition and across subject body sizes. We then propose a series of dependent measures to operationalize common research questions in psychological research. We present practical examples from several application areas to demonstrate the efficacy of our proposed method for full-body measurements and comparisons across time, space, body parts, and subjects.     

Effect of age on forward and backward digit spans

Abstract

A number of studies has suggested that aging is characterized by a decline in the central executive while the automatic processes (in particular operations by the phonological loop) remain intact. According to interpretation, age differences should be minimal in verbal forward digit span while they should be more important in backward verbal digit span. A sample of 1,000 subjects with ages ranging from 16 years to 79 years was used to test this hypothesis. the results show no significant effect of age on the difference between digit span forward and backward. the theoretical implications of these results are discussed.     

Negative life events and symptoms of depression and anxiety: stress causation and/or stress generation

Background and Objectives: Stressful life events are known to contribute to development of depression; however, it is possible this link is bidirectional. The present study examined whether such stress generation effects are greater than the effects of stressful life events on depression, and whether stress generation is also evident with anxiety. Design: Participants were two large age cohorts (N = 732 aged 44 years; N = 705 aged 63 years) from the West of Scotland Twenty-07 study. Methods: Stressful life events, depression, and anxiety symptoms were measured twice five years apart. Cross-lagged panel analysis examined the mutual influences of stressful life events on depression and on anxiety over time. Results: Life events predicted later depressive symptomatology (p = .01), but the depression predicting life events relationship was less strong (p = .06), whereas earlier anxiety predicted life events five years later (p = .001). There was evidence of sex differences in the extent to which life events predicted later anxiety. Conclusions: This study provides evidence of stress causation for depression and weaker evidence for stress generation. In contrast, there was strong evidence of stress generation for anxiety but weaker evidence for stress causation, and that differed for men and women.     

The impact of peer relations on academic progress in junior high

The purpose of this study is to examine whether peer relations within classrooms were related to students' academic progress, and if so, whether this can be explained by students' relatedness and engagement, in line with Connell and Wellborn's self-system model. We analyzed data of 18,735 students in 796 school classes in Dutch junior high schools, using multilevel analysis. Academic progress, conceptualized as regular promotion to the next year versus grade retention, moving upward, and moving downward in the track system, was measured at the time of transition between Grades 1 and 2 (equivalent to US Grades 7 and 8). The results indicated that students who were accepted by their peers had lower probabilities to retain a grade or to move downward in the track system. Although peer acceptance was associated with relatedness and engagement, these variables did not explain why peer acceptance was associated to academic progress. Furthermore, peer acceptance and relatedness were more strongly related in classes with more negative class climates.     

Perceptual and conceptual priming in patients with dissociative identity disorder

The present study examined implicit memory transfer in patients with dissociative identity disorder (DID). To determine priming impairments in DID, we included both several perceptual priming tasks and a conceptual priming task using neutral material. We tested a large sample of DID patients (n = 31), in addition to 25 controls and 25 DID simulators, comparable on sex, age, and education. Controls replicated conceptual priming results of Vriezen, Moscovitch, and Bellos (1995) by showing that conceptual priming seems to require the formation of domain-specific semantic representations, denoting either sensory or functional object attributes. We extended a study performed by Schacter, Cooper, and Delaney (1990) by demonstrating priming for impossible object using the sensitive priming index of response times. The simulators in the study were not able to simulate interidentity amnesia on the implicit memory tasks employed. Partly in contrast to participants in previous studies, DID patients showed evidence of perceptual priming as well as conceptual priming comparable to that of controls. DID patients thus displayed normal implicit memory performance.