PERCEPTUAL-MOTOR EXPLORATION AS A FUNCTION OF BIOMECHANICAL AND TASK CONSTRAINTS

Four experiments are reported that were designed to examine perceptual -motor exploration employed in determining the solution to a dual-axis positioning task under various biomechanical and task constraints. Ex periments 1, 2, and 3 used the two elbow joints to examine the impact of varying several geometric features of the relation between visual i nformation and action in this task. Experiment 4 examined the use of w ithin-limb, between-limb, and within-joint axes of motion in a similar task. The exploratory process was analyzed using a symbolic dynamic d efined over nominal categories of visual information and actions elici ted by the performer. The search strategy used to improve task perform ance was consistent across all the experimental manipulations imposed. The frequency pattern of nominal action categories demonstrated a pre ference for single-axis activity except in the within-joint condition which exhibited a preference for dual-axis activity. The pattern of pr eferred transitions among these action categories was also consistent across conditions, and lag sequential analysis revealed a robust tende ncy for cyclical activity in that opposite actions were often coupled in sequence. The topologically equivalent (extrinsic geometry) task sp aces led to qualitatively similar search strategies when considered at the level of action-information interaction (intrinsic geometry). The physical implementation of this strategy was strongly influenced by t he biomechanical constraints of the action system, while the manipulat ions of the geometric features of the action-information relation serv ed only to influence the quantitative properties of performance outcom e.