Abstract
When normal faces are rapidly presented in the visual periphery, they are perceived as grotesque and distorted. This phenomenon, “The flashed-face distortion effect” (FFDE) is a powerful illusion that may reveal important properties of how faces are coded in peripheral vision. Despite the strength of the illusion (and its popularity), there has been almost no follow-up work to examine what governs the strength of the illusion or to develop a clear account of its phenomenology. Presently, our goal was to address this by manipulating aspects of facial appearance and spatial/temporal properties of the flashed-face stimulus to determine what factors modulate the illusion’s strength. In three experiments, we investigated the extent to which local contrast (operationalized by the presence or absence of makeup), image eccentricity, image size, face inversion, and presentation rate of images within the sequence each contributed to the strength of the FFDE. We found that some of these factors (eccentricity and presentation rate) mattered a great deal, while others (makeup, face inversion and image size) made little contribution to the strength of the FFDE. We discuss the implications of these results for a mechanistic account of the FFDE, and suggest several avenues for future research based on this compelling visual illusion.
Highlights
Because distortion of facial appearance is the key outcome of the flashed-face distortion effect” (FFDE), the literature describing face distortion aftereffects[2] is a natural place to start trying to understand the mechanisms supporting the phenomenon
Could it be the case that the limited fidelity of peripheral vision plays a key role in the effect? Peripheral vision differs from central vision in a number of ways, and perhaps some of these differences offer a means of understanding the illusory percept, or help address some of the issues facing an account of the effect based on face distortion aftereffects
The Bayes Factor that we obtained for this main effect is in the range of “anecdotal” or “weak” evidence[27] in favor of the alternative hypothesis, which means that we cannot draw a strong conclusion regarding either the presence or absence of an effect. We suggest that this means that any effects of inversion on the FFDE are likely rather small, as an inconclusive Bayes Factor often indicates a lack of sufficient power to accept or reject the null hypothesis
Summary
Because distortion of facial appearance is the key outcome of the FFDE, the literature describing face distortion aftereffects[2] is a natural place to start trying to understand the mechanisms supporting the phenomenon. These aftereffects are typically obtained by asking observers to adapt to an image of a face that has been altered to have unrealistic feature proportions (e.g. an elongated nose), warped so that all facial features are compressed or expanded, or had facial features moved within the external contour into unrealistic locations (eyes placed very high in the head, e.g.). After viewing such a stimulus for several seconds or longer, observers typically report that unaltered faces appear distorted in an opposing manner, such that adapting to a compressed face will make a typical face look expanded. Peripheral vision is more sensitive to flicker than central vision, due to the faster responses of rods relative to cones[13]
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