Abstract
Visual material properties such as glossiness and lightness can only be perceived visually, and visual cues, such as image motion, have been found to contain potentially crucial information about visual material properties. Motion signals are generated, for instance, when we explore and manipulate objects with our hands, and previous work has found that motion cues contribute to the perception of gloss. Yet, little is known about the extent to which active exploration plays a role in the perception of visual material properties. Here, participants made judgments about the glossiness or lightness of objects in a virtual reality eye-tracking experiment. Participants were presented with 3D objects of five varying levels of glossiness or lightness. On a given trial, they had to either observe the stimulus passively or actively explore the object with their hand, during which their eye movements and hand trajectories were recorded. Following the exploration/observation, their task was to select the best-matched object from seven comparison objects. Overall we found that participants used different exploration behaviours to actively generate information when making judgments about different visual material properties. Specifically, we found that people spent longer observing, and explored objects to a greater extent when judging for gloss compared to when they were judging for lightness. Perhaps this is because participants had to rotate and observe the glossy objects from multiple orientations to obtain gloss information but for lightness, there is no particular informative orientation, hence they did not have to manipulate the object as much. Taken together, our results demonstrated that observers utilise a variety of exploratory behaviours to generate and acquire visual cues about different types of visual material properties.