The Effect of Practice on the Control of Rapid Aiming Movements: Evidence for an Interdependency Between Programming and Feedback Processing

The purpose of this experiment was to investigate how the control of aiming movements performed as fast and as accurately as possible changes with practice. We examined: (1) the influence of visual feedback on the initial impulse and error correction phases of aiming movements during acquisition; and (2) the effect of removing visual feedback at different levels of practice. Results from the acquisition trials indicated that vision had a major impact on the organization of the initial impulse and error correction phases. Also, consistent with findings from research involving temporally constrained movements, the cost of removing vision was greater after extensive levels than after moderate levels of practice. Collectively, these results denote the importance of visual feedback to the learning of this particular class of aiming movements. Learning appears to be a dual process of improved programming of the initial impulse and increased efficiency of feedback processing. Practice not only acts on programming and feedback processes directly, but also indirectly through a reciprocal interplay between these two processes.     

Liminality: the transforming grace of in-between places

Richard Rohr suggests that the only way out of a person's entrapment in "normalcy, the way things are," is to be drawn into sacred space, often called liminality, where he believes all genuine transformation occurs. Liminality, from the Latin word for threshold, is the state of being betwixt and between where the old world has been left behind but we have not yet arrived at what is to come. This article attempts to develop an understanding of liminality using metaphors of wilderness, tomb, and exile as found in the Jewish and Christian Scriptures. It seeks to reconcile the paradox of the apparent hiddenness of God and the concurrent opportunity to see Him in new ways that occurs in these times. Pastoral care and counseling applications for those working with people in liminal space are briefly engaged.     

A comparison of directly recorded and derived acceleration data in movement control research

This paper compares acceleration-time histories that were recorded during a simple arm extension/flexion movement completed as fast as possible and at a slower rate. Directly measured accelerations from an accelerometer were used to obtain an optimum filter cut-off frequency for displacement data were to be subsequently differentiated. Dependent variables such as ‘zero line crossings’ and ‘significant deviations’ were measured using both the accelerometer data and the derived acceleration data.