Motor learning of cue-dependent pull-force changes during an isometric precision grip task

The “raspberry task” represents a precision grip task that requires continuous adjustment of grip and pull forces. During this task subjects grip a specialized grip rod and have to increase the pull force linearly while the rod is locked. The aim of this study was to determine whether an associated, initially neutral cue is able to evoke pull-force changes in the raspberry task. A standard delay paradigm was used to study cued pull-force changes during an ongoing movement resulting in unloading. Pull force and EMG activity of hand and arm muscles were recorded from 13 healthy, young subjects. The cue was associated with a complex change in motor behavior.In this task, cued force changes take place more rapidly than in protective reflex systems (in median after the second presentation of the cueing stimulus). A cued force change was detectable in two-thirds of paired trials. Although the force change is produced by a decrease of the EMG activity in several grip- and pull-force-producing muscles, the most significant effect in the majority of the subjects was an increase of the activity of the flexor carpi ulnaris muscle which antagonises corresponding pull-force-producing muscles. Cued force changes require adequately and precisely controlled activation of the muscle groups involved in the movement.     

The development of sex typing: Themes from recent research

A conceptual framework for organizing the constructs and content areas included in research on sex typing is presented in this review of recent research on the development of sex typing. Two major themes are discussed. First, sex-typed play activities and interests emerge clearly in the first few years of life. Both play activities and peer preferences are sex typed earlier and more definitely than are personality traits and social behaviors such as aggression or dependency. It is suggested that researchers have underemphasized the importance of interests, activities, and peer associations while overemphasizing personality attributes as the core of sex typing. The second theme is that cognitions and concepts about sex typing are important in the acquisition of gender typing, but they are not sufficient by themselves for understanding the process by which sex-typed behavior is acquired. Children's sex-role concepts are sometimes related to their behavioral preferences, but other factors are also important influences on behavior.     

Ego development in perspective: Structural stage,functional phase,and cultural age-period models

Ego development is emerging as one of the more important areas of research in developmental psychology. This paper presents a structural stage approach to ego development and distinguishes it from two other models of ego development, which are termed functional phases and cultural ages. Two subtypes are also delineated within the structural stage approach—a monodomain and a multisubdomain—and the latter is argued for. These concepts are then illustrated through an analysis of four prominent ego development theories—those of Robert Selman, Robert Kegan, Jane Loevinger, and Erik Erikson. The important similarities and critical differences of the theories are clarified, which enables the authors to present a summary integration.     

Introduction: symposium on Brooke Ackerly’s Just Responsibility: A Human Rights Theory of Global Justice

ABSTRACT

This symposium brings together normative and empirical scholars in dialogue on Brooke Ackerly’s innovative and compelling recent monograph, Just Responsibility. Contributors discuss the book’s distinctive grounded normative theory methodology, its arguments for how individuals can take appropriate responsibility for global structural injustices, and its potential for practical impact.