Higher order and lower order variables in the visual perception of relative pulling force.

In 7 experiments, undergraduates judged the force exerted by a videotaped standing puller, a computer-generated (stick-figure) puller, or a computer-generated inverted pendulum. Single and stepwise multiple regression analyses determined the kinematic variables exploited by the participants. Results show that (a) judgments correlated highly with force and improved with feedback; (b) judgments correlated more highly with lower order kinematic variables than with force itself; (c) participants differed in the kinematic variables exploited; (d) participants changed over blocks of trials in the variables exploited; (e) some participants used compound kinematic variables; (f) the variables exploited depended on the type of feedback; and (g) judgments to upright pullers, inverted pullers, and simple pendula showed the same qualitative patterns. Implications for theories of direct perception, directed perception, and heuristics are considered.