Shape and motion interactions at perceptual and attentional levels during processing of structure from motion stimuli CNRS, UPR640 LENA, Laboratoire de Neurosciences Cognitives et Imagerie Cérébrale, Paris, France,& Université Pierre et Marie Curie-Paris6, Paris, France A. Miskiewicz Institut de Médecine Aérospatiale du Service de Santé des Armées, Brétigny sur Orge, France S. Buffat CNRS, UPR640 LENA, Laboratoire de Neurosciences Cognitives et Imagerie Cérébrale, Paris, France,& Université Pierre et Marie Curie-Paris6, Paris, France A.-L. Paradis CNRS, UPR640 LENA, Laboratoire de Neurosciences Cognitives et Imagerie Cérébrale, Paris, France,& Université Pierre et Marie Curie-Paris6, Paris, France J. Lorenceau This study uses a rapid-serial-visual-presentation (RSVP) paradigm to test the extent to which shape and motion direction can be independently accessed and processed during the perception of structure-from-motion (SFM) stimuli. Subjects reported the number of occurrences of shape or motion direction during RSVP sequences of 3D-SFM stimuli. Overall, performance was better for motion than shape. In the motion task, observers were less accurate when the motion direction was repeated revealing a repetition blindness (RB) effect. In addition, the repetition of shape, although irrelevant to the motion task, resulted in increased performance, without change in RB rate. In contrast, there was no RB at the group level in the shape task and the repetition of the irrelevant motion direction had no effect on the performance. A closer look at the data showed that observers fall in two statistically distinct groups for the shape task. Some observers (N = 6) show a repetition advantage (RA) while the others (N = 5) show a repetition blindness (RB) effect. No behavioral differences between groups could be found for the motion task. The implications of these results for models of SFM processing are discussed in the light of the type/token theory (N. Kanwisher, 2001). Keywords: 3D structure from motion, shape, motion, attention, RSVP, type, token Citation: Miskiewicz, A., Buffat, S., Paradis, A.<L., & Lorenceau, J. (2008). Shape and motion interactions at perceptual and attentional levels during processing of structure from motion stimuli. Journal of Vision, 8(16):17, 1–14, http://journalofvision. org/8/16/17/, doi:10.1167/8.16.17. Introduction Numerous studies (Kanwisher, Driver, & Machado, 1995; O’Craven, Downing, & Kanwisher, 1999; Treisman & Kanwisher, 1998) have investigated whether attention can be used to selectively process a specific dimension or feature of objects, such as their shape or color. Several studies (Fox & de Fockert, 2001; Harris & Dux, 2005; Kanwisher et al., 1995) have used an RSVP paradigm to study the dynamics and selectivity of attentional selection of a cued dimension through measures of repetition blindness (RB), which refers to a reduced capacity to report both occurrences of a repeated item during an RSVP sequence. One account of RB relies on the concept of “object file” (Kahneman, Treisman, & Gibbs, 1992; Kanwisher, 1991). While the recognition of an object would activate a “type,” successive occurrences of the same item would, or not in the case of RB, be recorded as different “tokens” or “object files.” RB can therefore be used to assess when two stimuli are considered as “the same object” by the visual system, providing insights into what defines an object file. Studies with letters, words, simple shapes, and colors, for which the cooccurrence of two dimensions were arbitrarily chosen (e.g., a red letter), have found that attention can select a single feature or dimension with little or no interference from other dimensions irrelevant to the task at hand (Kanwisher & Driver, 1992). On the other hand, studies with moving photographs of faces, houses, or drawings of objects have concluded that objectsVand their intricate dimen- sionsVare the units of attentional selection (Kanwisher Journal of Vision (2008) 8(16):17, 1–14 http://journalofvision.org/8/16/17/ 1 doi: 10.1167/8.16.17 Received July 10, 2008; published December 29, 2008 ISSN 1534-7362 * ARVO