Effect of disorientation on visual analysis, familiarity decision and semantic decision on faces

The disproportionate effect of vertical inversion on the processing of faces has often been interpreted as indicating differences in perceptive strategies between upright and inverted faces. If this is true, then the mathematical relation between the performance and the angular deviation would not be a linear function. Thirty subjects processed faces shown under 10 angular deviations from upright (0 deg) to upside-down (180 deg) in steps of 20 degrees, in a random design. Three cognitive levels (a between-subject factor) were tested, namely, gender classification of unfamiliar faces, familiarity decision on famous vs. unknown faces, and semantic decision (occupation) on famous faces, with 480 items per subject and task. We found no sign of a change of processing strategies for the upright vs. inverted presentations: a clear linear function emerged. However, the nature of the task could influence the effect of the angular deviation on the performance. Results suggest that, up to now, there is no definite proof of qualitatively different mechanisms underlying the processing of upright and inverted faces, respectively.