Search efficiency for tactile features rendered by surface haptic displays

Haptic interfaces controlled by a single fingertip or hand-held probe tend to display surface features individually, requiring serial search for multiple features. Novel surface haptic devices, however, have the potential to provide displays to multiple fingertips simultaneously, affording the possibility of parallel search. Using variable-friction surface haptic devices, we investigated the ability of participants to detect a target feature among a set of distractors in parallel across the fingers. We found that searches for a material property (slipperiness) and an illusory shape (virtual hole) were significantly impaired by distractors, while search for an abrupt discontinuity (virtual edge) was not. The efficiency of search for edges rendered by surface haptics suggests that they engage primitive detectors in the haptic perceptual system.