Time-to-Topple: Haptic Angular Tau

The temporal pattern of the force needed to rotate an object around a supporting edge at constant angular velocity is analyzed. We show that haptic angular tau, the momentary value of the force divided by its rate of change, specifies the time remaining until the object reaches its topple point, that is, its unstable equilibrium position. Previous analyses of ratios of this general form, the inverse of the relative rate of change of a variable, have shown the availability of acoustic and visual information for the time-to-contact between a moving object and a station point, and acoustic information for vessel-filling. The present results document the availability of haptic information for a noncontact event and suggest that the tau analysis of physical variables may be a fruitful tactic in perceptual studies of many types of events.