|Are Local Changes in Faces Really Local?|
|Michael D. Anes, Nicholas A. Del Grosso, Darcy Dubuc
Department of Psychology, Wittenberg University
|In Anes, Short & Storer (VSS08), brief face presentations with an inverted eye (but not eyebrow) in the LVF resulted in greater bizarreness ratings than RVF inverted eye presentations. In Experiment 1 of the present study, participants (n=15) viewed an unaltered target face, then a 120 ms exposure of a probe face, and indicated whether the probe was the same as the target. Same judgment RTs increased for LVF eye inversions (648 ms) relative to unaltered faces (604 ms, t=3.49, p<.01) and RVF eye inversions (608 ms, t=2.39, p<.05). Local and/or global relational information disrupted by Thatcherizing an eye appears to be more efficiently encoded by the right hemisphere, resulting in both elevated bizarreness ratings and same judgment RTs.
We address recent work by Goffaux and colleagues in which independent manipulations of interocular distance and vertical eye position (∆=15 pixels) were made. In these studies, the RH is quite sensitive to vertical displacement of the eyes and the LH is sensitive to horizontal displacement and feature changes. In Experiment 2 here, stimuli with one eye moved out or down (∆ = 3 or 6 pixels, with the eyebrow position fixed) were presented in the same/different task. We hypothesized that RVF horizontal manipulations and LVF vertical manipulations would increase same judgment RTs over those for unaltered faces, but observed no visual field by manipulation interaction. Same judgment RT increases after 3 pixel displacements tended to be higher in the RVF than LVF. Conversely, 6 pixel displacements in the LVF resulted in greater same judgment RT increases than in the RVF. Are small vertical or horizontal changes more local and LH-mediated while slightly larger changes are local and global and RH-mediated? In another planned experiment we will move the eye and eyebrow together to maintain local relations while disrupting global configuration.
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