Scaling Judgments of Lifted Weight: Lifter Size and the Role of the Standard

Abstract

Runeson and Frykholm (1981, 1983) discovered that observers could judge the amount of weight lifted by another person when only the motions were visible in patch-light displays. Gilden and Proffitt (1989) suggested that this might have been experimental artifact. A standard had been included and might have been used to scale perceived motions to amounts of lifted weight. Were standards essential to the results? We performed experiments to investigate the role of the displays, of a standard, of haptic experience of a known weight, and of information about lifter size. The results demonstrated that haptic experience of a known weight and standards were equivalent in reducing random errors, but that standards, unlike haptic information, produced a contraction effect that increased systematic errors. Results without a standard were comparable to those of Runeson and Frykholm. Observers also judged displays of three different-size lifters, each lifting max- imum weights equal to a third of their body size. Static information for lifter size was controlled and no standard was used. Results demonstrate that the lifted- weight result is not experimental artifact.