Gestalt grouping effects on tactile information processing: when touching hands override spatial proximity.

Using a tactile variant of the negative-priming paradigm, we analyzed the influence of Gestalt grouping on the ability of participants to ignore distracting tactile information. The distance between participants' hands, to which the target and distractor stimuli were simultaneously delivered, was varied (near/touching hands vs. hands far apart). In addition, the influence of touching hands was controlled, as participants wore gloves and their hands were blocked from vision by a cover. The magnitude of the tactile negative-priming effect was modulated by the interaction between hand separation and whether or not gloves were worn. When the hands were touching, negative priming emerged only while wearing gloves that prevented direct skin-to-skin contact. In contrast, when the separation between the participants' hands was larger, negative priming emerged only when gloves were not worn. This pattern of results is interpreted in terms of the competing influences of two interacting Gestalt principles--namely, connectedness and proximity--on the processing of tactile distractors.