This study investigates the organization of upper body coordination in tasks involving complex visual and manual demands. In the past, bimanual coordination has been approached in the context of symmetric or asymmetric interactions of the two hands. But routine behavior associated with work tasks requires synchronization in time and space of multiple components across multiple concurrent actions. Hence the problem of upper body coordination involves a combination of both symmetric and asymmetric modes of interaction, with a dynamic switching between the two. Although current models may explain the two modes of interaction individually, none of the existing models account for an integration of the two modes from the perspective of task performance. A pilot study was conducted in which subjects performed assembly tasks involving object transfers and manipulations with varying levels of visual and manual demands and performance constraints, such as speed and precision. The preliminary results indicate that among the many different ways in which motor tasks can be performed, the sequencing of movement components is largely influenced by the tendency to maximize synchronization between the 2 hands within the limits of task and resource constraints. Yet, hand movements are almost never concluded simultaneously, and it seems that visual feedback resources limit parallel performance of even purely symmetric motor tasks. There is always a trade-off between the precision demand of the task and the extent of affordable symmetric, parallel performance. High precision or high visual demand of task increases movement duration and also lengthens the final closed-loop phase of movements. This study is the first step in building a model that would be able to simulate any routine one/two-handed object manipulation task.
