Effects of initial limb position on the accuracy, reaction time and electromyographic patterns of rapid movements

An experiment was performed to determine the effects of initial limb condition on final accuracy of rapid, elbow flexion movements in the horizontal plane. Electromyographic (EMG) recordings were also taken from an agonist (biceps) and antagonist (triceps) muscle by means of bipolar surface electrodes. In the experiment the subject's forearm was passively oscillated by means of an electric motor, and when an auditory buzzer sounded, the subject was required to react as quickly as possible and rapidly move to the previously learned target angle. Thus, movements could be initiated from either static or moving starting positions. The results indicated that general accuracy was not greatly affected by these manipulations, however, constant error and pre-motor reaction time suggested that subjects may have been utilizing initial limb condition information contrary to a mass-spring view. EMG data showed that the timing characteristics of the agonist and antagonist muscles were modulated, depending on the type of movement produced, supporting an impulse-timing model (Wallace 1981).     

The response cost lottery: A time efficient and effective classroom intervention

An ABAB design was used to evaluate the effect of a response cost lottery procedure on the percentage of on-task behavior and accuracy of academic work of three fourth-grade students. Although contingencies were attached primarily to behavior, both on-task behavior and academic performance measures increased in treatment conditions. Teacher reports indicated the intervention was both easy to use and effective.     

Some suggestions for modifying the incremental influence of organizational members

The purpose of this series of three studies was to examine ways of modifying incremental influence. The first was an experimental laboratory study involving manipulation of interpersonal attraction via perceptions of similarity. Results from Study I strongly supported the hypothesis that referent power can be changed as a function of interpersonal attraction. Study II reports on an organizational simulation and provides further evidence for the linkage between interpersonal attraction and referent power. This study also tested the hypothesis that satisfaction covaries with self-perceived referent power. The data, while supporting the hypothesis, expanded the association of satisfaction to the other power bases, i.e., expert, reward, coercive, and legitimate. The final study examined power changes as a function of organization development interventions in a field setting. The findings show that not only was referent power enhanced, as hypothesized, but that other power bases also changed. In addition, hypotheses previously tested in Studies I and II received further confirmation in Study III. The overall pattern of results suggests that referent power can be altered by affecting the interpersonal attraction of group members. Implications for organizational intervention and practice are discussed, and some possible modifications to the theoretical framework of power are advanced.     

The emergence of representation in search: Understanding the hider as an independent agent

Corrigan's results point the way toward a reconceptualization of how the development of representation affects search. The child does not cognitively recreate the invisible displacements of the object. Instead she seems to understand that the hider is an independent agent who can use simple hiding strategies that the child does not directly perceive. This representational skill for search, we propose, is one realization of a general representational capacity that emerges late in the second year. The general capacity is defined structurally as the ability to coordinate two sensorimotor systems into a single skill. Although there seem to be some discontinuities in the emergence of the representational capacity, its development is mostly gradual and continuous.