Interplay of biomechanical constraints and kinematic strategies in selecting arm postures

In this study, the authors examined the interplay between biomechanics and control strategies in the resolution of excess degrees of freedom at the joint level. Seven participants made aimed arm movements from 30 starting points and several starting postures to targets. Final arm postures for movements to a target exhibited substantial joint angle variation. Through regression modeling and by comparing observed final arm postures with biomechanically plausible postures, the authors identified 3 kinematic strategies: (a) Maintain deviations from the average angle at the starting point to the joint's final posture; (b) make torso rotations that are a fixed proportion of shoulder rotations; and (c) adopt a characteristic combination of 4 wrist-positioning approaches. The results demonstrated that kinematic strategies can account for substantial variance in final arm postures, if one takes into account 2 types of individual differences-those that arise inevitably from biomechanical constraints and those that reflect choices in movement strategy.     

Planning and executing simple movements: contributions of relative-time and overall-duration specification

In 3 experiments, the authors used a precuing protocol to examine the nature and cost of programming and the subsequent reprogramming of a movement's relative time and overall duration. Initial programming followed a fixed-order specification; knowledge of the necessary relative time was required before information regarding overall duration could be used in a manner that expedited response planning. In the case of reprogramming, however, when a modification had to be made in either the relative time or overall duration of the anticipated and already-prepared response, performers chose to completely reprogram the entire response. Complete reprogramming occurred even when the performer had correctly prepared the higher order relative-time component and only had to modify the overall duration of the movement. The data indicate that organizing movement timing before movement initiation is accomplished in a fundamentally different manner depending on whether the movement is being initially compiled or modified.     

A functional MRI study of human amygdala responses to facial expressions of fear versus anger

Functional magnetic resonance imaging (fMRI) of the human brain was used to compare changes in amygdala activity associated with viewing facial expressions of fear and anger. Pictures of human faces bearing expressions of fear or anger, as well as faces with neutral expressions, were presented to 8 healthy participants. The blood oxygen-level dependent (BOLD) fMRI signal within the dorsal amygdala was significantly greater to Fear versus Anger, in a direct contrast. Significant BOLD signal changes in the ventral amygdala were observed in contrasts of Fear versus Neutral expressions and, in a more spatially circumscribed region, to Anger versus Neutral expressions. Thus, activity in the amygdala is greater to fearful facial expressions when contrasted with either neutral or angry faces. Furthermore, directly contrasting fear with angry faces highlighted involvement of the dorsal amygdaloid region.     

Maternal behavior, paternal behavior, and pup survival in CD-1 albino mice (Mus musculus) in three different housing conditions

Parental behavior, food consumption, and pup development in litters of CD-1 albino mice (Mus musculus) with single mothers or paired mothers in 3 different housing conditions were compared. Fewer pups survived when parents were required to run in a wheel to obtain food, and these pups had lower weights than pups in the wheel-noncontingent and no-wheel groups. The presence of the male facilitated pup survival in the wheel-contingent group but had no effect on pup growth. Mice in the wheel-contingent group ran more revolutions than those in the wheel-noncontingent group and spent less time in parental care. In the wheel-contingent group, males spent more time running and ate less food than females, suggesting that males may indirectly facilitate pup development by providing food for the mother. The results suggest that the presence of the male increases pup care and may facilitate maternal behavior under appropriate environmental conditions.     

Developmental Trends in False Memory Across Adolescence and Young Adulthood: A Comparison of DRM and Memory Conformity Paradigms

Little is known about the reliability of eyewitness memory among adolescents as most memory research has focused primarily on adults and young children. A number of studies recently have emerged outlining conditions where memory suggestibility increases from early childhood to adulthood. These developmental reversals are found in semantic association tasks such as the Deese–Roediger–McDermott (DRM) paradigm and have not yet been thoroughly investigated among adolescents. In the current study, we examined DRM performance among 11–21 year olds (N = 245). Extending the work comparing children and adults, false memory on the DRM task increased with age. False memory on the DRM task was not associated with false memory on a memory conformity task. The different memory processes involved with the tasks and the implications for legal psychology are discussed. Copyright © 2015 John Wiley & Sons, Ltd.