JUDGING ROLLING WHEELS - DYNAMIC AND KINEMATIC ASPECTS OF ROTATION - TRANSLATION COUPLING

Four experiments were carried out to investigate observers' abilities to judge rolling motions. The experiments were designed to assess whet her two important aspects of such motions are appreciated: the kinemat ic coupling of rotation and translation, and the dynamic effects of gr avity. Different motion contexts of rolling wheels were created using computer-generated displays. The first experiment involved wheels roll ing down an inclined plane. Observers spontaneously appreciated the an omaly of wheels that failed to accelerate, but they were not able to d ifferentiate between different acceleration functions. Moreover, their judgments were almost exclusively based on the translation component of the rolling motion, neglecting the rotation component. In a second experiment it was found that observers could accurately estimate the p erimeter of various objects. Thus, their inability to consider rotatio n information is not attributable to misperceptions of the geometry of wheels. In a third experiment the finding that rolling wheels appear to overrotate was replicated; however, findings from this experiment a lso showed, together with those from a fourth experiment, that observe rs are able to make very accurate judgments about translation-rotation coupling in rolling wheels when information is provided about the ori entation of the wheel and the texture of the surface on which it rolls .