The many dimensions underlying perceived softness: How exploratory procedures are influenced by material and the perceptual task*

Haptic research has traditionally often equated softness with compliance. However, in a recent study we have suggested that compliance is not the only perceived object dimension underlying what is commonly called softness [1]. Here, we investigate how the different perceptual dimensions of softness affect how materials are haptically explored. Participants freely explored and rated 19 materials on 15 adjectives. The adjectives defined different perceptual tasks by being associated with different softness dimensions. Materials were chosen to represent extreme values separately for each dimension; some materials served as control. Hand movements were recorded on video and subsequently categorized into different exploratory procedures (EPs). A multivariate analysis of variance (MANOVA) yielded significant effects of material, of the perceptual task and of their interaction. Taken together, the results suggest that participants actively adapt their EPs to both the type of material being explored, and to the judged softness dimension, and thus support the notion of different dimensions of softness.