Material discrimination relies on context-dependent active sensing strategies

Material perception is typically studied under passive and highly constrained viewing conditions, thus leaving it unclear whether humans rely on active sampling strategies to resolve perceptual ambiguities. In everyday vision, however, observers naturally move their heads and manipulate objects with their hands to obtain informative cues, thus raising the question of how such exploratory actions contribute to material discrimination. We used immersive virtual reality to examine whether viewpoint changes and object manipulations support the discrimination of visually challenging materials, specifically metal versus glass, whose appearances depend strongly on the associated illumination and viewing geometry. Across three experiments, we found that observers increased the amount of exploratory movements-specifically, viewpoint changes and object manipulations-when the material identity was ambiguous, and that a greater amount of exploration was associated with higher discrimination performance. By independently manipulating head- and hand-based motions, we identified the context-dependent contributions of each movement type; viewpoint changes dominated when multiple objects could be compared simultaneously, whereas object manipulation was more effective when only a single target was available. Moreover, the participants differed in the effectiveness of their sampling strategies, with variation in discrimination sensitivity reflecting both individual differences in strategy and changes over time. Together, these findings demonstrate that material discrimination depends on flexible, context-dependent active exploration rather than passive evaluation of static images. By dissociating head- and hand-based exploration, our study clarifies how observers select actions that generate diagnostic visual information for material discrimination.