Abstract
An extremely well replicated patterning in picture-plane rotation object recognition time functions is a dip from about 135° to 225° that reaches a local minimum at 180°. Two experiments were conducted to determine why there is a counter-intuitive local improvement in recognition performance when object images are inverted. Experiment 1 used naturally occurring, everyday objects in a vocal identification task to assess the effects of picture-plane rotation (either 0°, 90°, 180°, or 270°) on reaction times and error rates. Stimuli were selected strategically and presented one at a time. Performance varied according to the spatial configuration of an object’s visual features. Objects with only side-of part relations evinced the characteristic M-shaped rotation function, with planned contrasts for reaction times and error rates revealing the dip at 180°. In contrast, for objects with an above-below spatial organization of parts, recognition functions demonstrate a positive monotonic relationship between identification difficulty and deviation from the canonical orientation (i.e., 0°). Planned contrasts for reaction times and error rates revealed a peak at 180° in the rotation functions for the above-below objects. Experiment 2 employed a brief-exposure sequential matching paradigm (same or different task) and a novel set of artificial objects displayed at one of the four aforementioned rotations to control for previous exposures and potential extraneous variables associated with naming naturally occurring objects. Again, planned contrasts revealed that rotation functions critically depend on the type of categorical relationship between the visual features of an object. The dip only occurred for inverted side-of objects and not for inverted above-below objects. Together, these experiments suggest that the restoration of categorical spatial relations upon picture-plane inversion facilitates recognition performance and that basic-level object structural representations are encoded to generalize to mirror reflections in the lateral plane which preserve canonical above-below relations.