The Role of Exploratory Procedures in Perceiving Affordances in a Bimanual Wielding Task

Properties like the weight and length of wielded objects can be judged without vision. Previous studies have investigated perceptual information, like the moment of inertia, specifying such object properties by wielding with one hand. The current study extends this work by investigating how blindfolded participants bimanually heft and wield objects to perceive the weight or length. Participants were presented with rods, with weights attached either symmetrically on both sides of the center, or asymmetrically. The magnitude of weights attached and their position on the rod were also manipulated. Blindfolded participants were asked to either judge the weight or length of a set of rods, after they actively wielded each rod. Participants' muscle activity and exploratory movements were tracked. We investigated whether the temporal pattern of movements and muscle activity differed, depending on their intention to perceive rod weight or length. As expected, participants wielded the rods differently, depending on whether they were judging the weight or length. Additionally, weight distribution, the magnitude, and the position on the rod where the weights were attached, affected perceived heaviness. Surprisingly, none of these factors affected the perceived length of the rod, indicating the availability of perceptual information other than the moment of inertia.