Abduction, adduction and hand differences in simple and serial movements

Abductive or adductive movements were made either towards single targets left or right of “home”, or sequentially from target to target with various levels of advance information. In the former situation the preferred hand completed responses (movement time, MT) faster than the non-preferred, while the non-preferred hand initiated them faster (reaction time, RT); these effects were in both cases stronger with harder (knob turn) than with easier (touch) responses. Abductive responses (MTs, not RTs) were faster than adductive, especially with the preferred right hand. However in the sequential task adductive responses were the faster, consistently so by MTs, while with respect to time spent motionless at each target (down time, DT) more so with the non-preferred hand, and under conditions of maximal advance information. Findings were discussed in the contexts of movement complexity, hemispatial representation, and how advance information may be utilized in the resolution of directional uncertainty. There may be an evolutionary advantage in making complex manipulative responses adductively, close to the body, while reaches are usually made abductively, to the periphery of circumcorporeal space.