PERCEPTION OF KINEMATIC CHARACTERISTICS IN THE MOTION OF LIFTED WEIGHT

It has been widely shown that human observers are able to perceive lif ted weight from the observation of a point-light display of the lifter 's action. In the experiments reported here, the kinematic information used by observers to perceive a lifted weight was determined. In Expe riment 1, observers (N = 30) were able to identify weights (5, 10, 15, 20, and 25 kg) successfully by observing only the lift phase of the a ction. Other procedures, such as walking while holding the weight and placing the weight on a table, did not result in significantly improve d estimations. In Experiment 2, the kinematic patterns used by 4 Lifte rs with weights varying from 5 to 25 kg were examined. Changes in weig ht lifted resulted in changes in lift velocity, hip angle, and dwell t ime. In Experiment 3, in which 15 observers participated, these 3 kine matic variables were experimentally manipulated. The results indicated that observation was most significantly influenced by variations in l ift velocity. The results are discussed in relation to kinematic speci fication of dynamics and heuristic approaches.