Divergent representations of manipulable and non-manipulable objects revealed with repetition blindness

Abstract

Neuroimaging and neuropsychological studies suggest that manipulable objects (i.e., objects associated with particular actions) have distributed representations that reflect not only their visual features but also the actions they afford. This study used rapid serial visual presentation (RSVP) to investigate the nature of the representations underlying identification of manipulable objects. When stimuli are presented at RSVP rates, items repeated within 500 msec of each other are frequently missed, a phenomenon known as repetition blindness (RB). RB is thought to occur because repeated stimuli activate the same abstract memory representation (type) but are not individuated into distinct visual episodes (tokens) due to the spatio-temporal constraints of RSVP. In two experiments that employed different stimulus sets (photographs vs line drawings), observers viewed RSVP streams containing three objects and six masks and attempted to identify the objects. The first and third objects in the stream were either the same object repeated, or distinct objects, and were either Action (i.e., manipulable) or Non-Action (non-manipulable) objects. There were two main findings. First, joint accuracy for reporting two distinct Action objects was considerably lower than for Non-Action objects, even when the two object classes were equated in terms of ease of identification. Second, whereas Non-Action objects induced RB independent of the objects' orientation, in keeping with previous findings (Harris & Dux, 2005; Hayward et al., in press), there was no RB at all for Action objects. Instead, significant priming was obtained when an Action object was repeated in the same orientation. Taken together, these findings implicate independent sources of visual and motor information, which require integration for successful identification. Under RSVP conditions, this renders Action objects vulnerable to interference from other objects associated with conflicting motor programs, but facilitates individuation of repeated objects associated with the same action.