The Effect of Paired Muscle Stimulation on Preparation for Movement

Paired muscle stimulation is used clinically to facilitate the performance of motor tasks for individuals with motor dysfunction. However, the optimal temporal relationship between stimuli for enhancing movement remains unknown. We hypothesized that synchronous, muscle stimulation would increase the extent to which stimulated muscles are concurrently prepared for movement. We validated a measure of muscle-specific changes in corticomotor excitability prior to movement. We used this measure to examine the preparation of the first dorsal interosseous (FDI), abductor digiti minimi (ADM), abductor pollicis brevis (APB) muscles prior to voluntary muscle contractions before and after paired muscle stimulation at four interstimulus intervals (0, 5, 10, and 75 ms). Paired muscle stimulation increased premovement excitability in the stimulated FDI, but not in the ADM muscle. Interstimulus interval was not a significant factor in determining efficacy of the protocol. Paired stimulation, therefore, did not result in a functional association being formed between the stimulated muscles. Somatosensory potentials evoked by the muscle stimuli were small compared to those commonly elicited by stimulation of peripheral nerves, suggesting that the lack of functional association formation between muscles may be due to the small magnitude of afferent volleys from the stimulated muscles, particularly the ADM, reaching the cortex.     

Modeling Dependence Structures for Response Times in a Bayesian Framework

A multivariate generalization of the log-normal model for response times is proposed within an innovative Bayesian modeling framework. A novel Bayesian Covariance Structure Model (BCSM) is proposed, where the inclusion of random-effect variables is avoided, while their implied dependencies are modeled directly through an additive covariance structure. This makes it possible to jointly model complex dependencies due to for instance the test format (e.g., testlets, complex constructs), time limits, or features of digitally based assessments. A class of conjugate priors is proposed for the random-effect variance parameters in the BCSM framework. They give support to testing the presence of random effects, reduce boundary effects by allowing non-positive (co)variance parameters, and support accurate estimation even for very small true variance parameters. The conjugate priors under the BCSM lead to efficient posterior computation. Bayes factors and the Bayesian Information Criterion are discussed for the purpose of model selection in the new framework. In two simulation studies, a satisfying performance of the MCMC algorithm and of the Bayes factor is shown. In comparison with parameter expansion through a half-Cauchy prior, estimates of variance parameters close to zero show no bias and undercoverage of credible intervals is avoided. An empirical example showcases the utility of the BCSM for response times to test the influence of item presentation formats on the test performance of students in a Latin square experimental design.

     

Histoire et tendances de la psychologie critique en Amérique du Nord

Critical psychology in the United States and Canada identifies psychology as inherently a political enterprise. It has developed along three overlapping but distinct lines that diverge in history, focus, and purpose: (a) building on psychology's empirical research methods, employing them to help reduce injustice and advance progressive or radical social change; (b) rejecting mainstream psychology's positivist and individualistic theoretical and empirical underpinnings and developing emancipatory theory and practices in their place; and (c) challenging psychology's institutional power over individuals, especially mentally and emotionally troubled individuals whose behavior strikes others as problematic. This article first describes each approach's history, influences, and roles in academic scholarship and institutions and in professional and nonacademic organizations. It then details recent efforts to expand and institutionalize a critical psychology presence despite mainstream North American psychology's strong resistance, while noting the central intertwining of personal networks, political leanings, and psychological theory. Finally, it briefly considers the implications and consequences of the lack of consensus about what critical psychology is and should become.     

The Development of Self-Control of Emotion: Intrinsic and Extrinsic Influences

In this paper, we review evidence that supports the notion that intrinsic and extrinsic factors contribute to the development of self-control of emotions. Intrinsic factors include the infant's temperament, and cognitive processes such as attention and inhibitory control. Extrinsic factors involve the caregiving environment, sibling and peer relationships, and cultural expectations regarding emotional displays. Integrative approaches to the study of the development of self-control of emotion will be most fruitful if investigations examine the interplay, over time, among these internal and external factors.     

Mass Murder: An Analysis of Extreme Violence

Mass murder involves the slaughter of four or more victims by one or a few assailants within a single event, lasting but a few minutes or as long as several hours. More than just arbitrary, using this minimum body count—as opposed to a two- or three-victim threshold suggested by others (e.g., Ressler et al., 1988, Holmes and Holmes, 2001)—helps to distinguish multiple killing from homicide generally. Moreover, by restricting our attention to acts committed by one or a few offenders, our working definition of multiple homicide also excludes highly organized or institutionalized killings (e.g., war crimes and large-scale acts of political terrorism as well as certain acts of highly organized crime rings). Although state-sponsored killings are important in their own right, they may be better explained through the theories and methods of political science than criminology. Thus, for example, the definition of multiple homicide would include the crimes committed by Charles Manson and his followers, but not those of Hitler's Third Reich, or the 9/11 terrorists, despite some similarities in the operations of authority.     

Effects of Computer-Based Fluency Training on Concept Formation

This study provides a preliminary analysis of how the techniques of fluency training can be combined with systematic concept instruction to improve the learning of complex verbal concepts. Fluency techniques, which require the learner to respond accurately at high rates, have typically focused on definition learning when teaching concepts. Instructional psychologists, however, recommend multiple exemplar training for conceptual instruction. To examine this issue, 41 undergraduate students completed a computer-based instructional module on logical fallacies. Participants were assigned to one of four groups, with the modules for each group differing only in the type of practice provided—either fluency or practice with either examples or definitions. Examination of posttest scores revealed significantly higher scores for participants in the examples groups than those in the definitions groups, but low experimental power prevented a clear conclusion to be drawn about differences between the fluency and practice groups. Implications of results and several methodological issues relevant to this area of research are discussed.     

Framing and Risky Choice as Influenced by Comparison of One's Achievements with Others: The Case of Investment in the Stock Exchange

Based on social comparison theory and equity theory, the first aim of this study was to examine the hypothesis that framing is affected not only by previous success or failure, but also by comparisons with relevant others' outcomes as well. The second aim of the study was to examine prospect theory propositions that people are risk aversive for gains and risk seeking for losses. A total of 220 students were administered scenarios that described outcomes of their stock investments (gains or losses). In addition, they were provided with information about their close friends' outcomes investing in similar stocks. Generally, the hypothesis regarding the influence of others' outcomes on framing was confirmed. However, results showed that, in contradiction to prospect theory, gain framing rather than loss framing was related to risk seeking behavior. Specifically, in the gain framing situation, the readiness to take risks was highest when the others' outcomes were equal to those of the participants. The limitations of prospect theory are discussed.     

Linking Gene, Brain, and Behavior: DRD4, Frontal Asymmetry, and Temperament

ABSTRACT— Gene-environment interactions involving exogenous environmental factors are known to shape behavior and personality development. Although gene-environment interactions involving endogenous environmental factors are hypothesized to play an equally important role, this conceptual approach has not been empirically applied in the study of early-developing temperament in humans. Here we report evidence for a gene- endo environment (i.e., resting frontal brain electroencephalogram, EEG, asymmetry) interaction in predicting child temperament. The dopamine D4 receptor (DRD4) gene (long allele vs. short allele) moderated the relation between resting frontal EEG asymmetry (left vs. right) at 9 months and temperament at 48 months. Children who exhibited left frontal EEG asymmetry at 9 months and who possessed the DRD4 long allele were significantly more soothable at 48 months than other children. Among children with right frontal EEG asymmetry at 9 months, those with the DRD4 long allele had significantly more difficulties focusing and sustaining attention at 48 months than those with the DRD4 short allele. Resting frontal EEG asymmetry did not influence temperament in the absence of the DRD4 long allele. We discuss how the interaction of genetic and endoenvironmental factors may confer risk and protection for different behavioral styles in children.     

Neural Correlates of Reward Processing in Adolescents With a History of Inhibited Temperament

ABSTRACT— Functional imaging data were acquired during performance of a reward-contingency task in a unique cohort of adolescents (ages 14–18 years) who were characterized since infancy on measures of temperamental behavioral inhibition. Neural activation was examined in striatal structures (nucleus accumbens, putamen, caudate) with a known role in facilitating response to salient reward-related cues. Adolescents with a history of behavioral inhibition, relative to noninhibited adolescents, showed increased activation in the nucleus accumbens when they believed their selection of an action would affect reward outcome. Neural responses did not differ between the two groups when participants made a prespecified response that they knew would result in reward or when they produced random motor responses that they knew would not be rewarded. These results link inhibited temperament and perturbed neural responses to reward-contingency cues.