Abstract
Previous research has shown that object recognition may be either orientation-dependent, or orientation-invariant, depending on a variety of stimulus and task variables. This study investigated the role of polar features (i.e., stimulus features that may serve to define the directionality of an object-based spatial reference frame) to the computation of orientation-invariant shape representations. A recognition memory paradigm was used to examine the effects of stimulus orientation on the recognition of previously memorised 2D novel shapes. The salience of the internal shape axes and polar features were manipulated. The results of Experiment 1 confirmed that orientation-invariant recognition can be found from the outset of testing with objects containing a salient internal axis of symmetry. In Experiments 2 and 3 it was found that the removal of a single salient polar feature, whilst preserving the axis of elongation, was sufficient to increase stimulus orientation effects. This finding suggests that polar features may play an important role in object constancy. It is suggested that polar features act by facilitating the assignment of consistent coordinate values to the spatial locations of features in shape representations encoded within object-based reference frames.
The work reported in this study was supported by project grant 5/S15963 (BBSRC, UK) awarded to ECL.