An experimental paradigm to compare motor performance under laboratory and under everyday-like conditions.

Research findings on human motor skills may not necessarily hold in everyday life, since laboratory and everyday scenarios typically differ with respect to the subjects' attention to the skill, their motivation to perform at their best, the goals they try to achieve, and the mode of movement initiation - extrinsic versus intrinsic. Here we present an experimental approach which can be used to substantiate the hypothesized effects of laboratory (L) versus everyday (E) settings on one type of motor skill, i.e., manual prehension. This approach is based on two tasks: In task L, subjects are told that they will participate in an experiment on grasping, and are instructed to seize and move a lever upon appearance of a visual target. In task E, they are told that they will play a computer game, and they have to seize and move the lever in order to proceed from one game level to the next. Both tasks include prehension movements from the same starting position and object to the same terminal position and object; movements differ only in their behavioural context. We exemplify the utility of our approach with a preliminary analysis of kinematic and force data. It shows that the two tasks differ with respect to several performance measures, and that some performance measures make independent contributions to that difference. The existence of independent contributions suggests that behavioural context may influence prehension via several distinct routes. Our approach can be used for comprehensive analyses of the context-dependence of motor skills in various reference groups.