Abstract
Corballis (1988) speculated that recognition of rotated shapes could occur on the basis of viewpoint-invariant information, while viewpoint-dependent information may be used to double check the initial identification and determine the orientation of the object in space. Recent experiments using rapid serial visual presentation (RSVP) support this idea. Harris and Dux (2005) and Corballis and Armstrong (2007) have shown that processing of object identity, as indexed by repetition blindness, is largely orientation-invariant, but that object orientation is also extracted rapidly and can modulate the ease with which objects are individuated. The findings of these RSVP studies suggest that object identity and orientation are initially processed independently, but are then bound together into a conscious percept. In the present study, participants viewed short RSVP streams consisting of two line drawings of familiar objects, presented sequentially for 70 ms each in different orientations (all possible pairs of 90, 180 and 270 deg), which were preceded and followed by pattern masks. Before each trial, participants were cued with an object and had to decide whether that object was present on the trial and then report its orientation. The results indicate that object identity was extracted more reliably than object orientation and that correct judgement of object orientation was contingent on correct identification of the object. The more interesting observation is that when participants gave an incorrect orientation response, they were significantly more likely to report the orientation of the other object presented on that trial than an orientation that was not present. Thus, it appears that object identity is determined independently of orientation and that establishing the object's orientation is a later process that can be prone to incorrect conjunctions between the features of competing objects.
This work was supported by ARC grant DP0557590 to I. Harris and M. Corballis.