Orientation-Contingent Face Aftereffects and Implications for Face-Coding Mechanisms

Abstract

Humans have an impressive ability to discriminate between faces despite their similarity as visual patterns. This expertise relies on configural coding of spatial relations between face features and/or holistic coding of overall facial structure. These expert face-coding mechanisms appear to be engaged most effectively by upright faces, with inverted faces engaging primarily feature-coding mechanisms. We show that opposite figural aftereffects can be induced simultaneously for upright and inverted faces, demonstrating that distinct neural populations code upright and inverted faces. This result also suggests that expert (upright) face-coding mechanisms can be selectively adapted. These aftereffects occur for judgments of face normality and face gender and are robust to changes in face size, ruling out adaptation of low-level, retinotopically organized coding mechanisms. Our results suggest a resolution of a paradox in the face recognition literature. Neuroimaging studies have found surprisingly little orientation selectivity in the fusiform face area (FFA) despite evidence that this region plays a role in expert face coding and that expert face-coding mechanisms are selectively engaged by upright faces. Our results, demonstrating orientation-contingent adaptation of face-coding mechanisms, suggest that the FFA's apparent lack of orientation selectivity may be an artifact of averaging across distinct populations within the FFA that respond to upright and inverted faces.

Sex-contingent face after-effects suggest distinct neural populations code male and female faces

“…For example, adaptation to faces with contracted features causes novel faces with contracted features to be perceived as more normal than prior to this exposure (Rhodes et al 2003;Rhodes et al 2004). Analogous visual after-effects have been observed following exposure to faces varying in identity (Leopold et al 2001;Rhodes et al 2001) ethnicity (Webster et al 2004), sex (Rhodes et al 2004;Webster et al 2004), and expression (Webster et al 2004). Adaptation from exposure to faces also influences attractiveness judgments potentially due to the positive association between perceived normality and attractiveness (Halberstadt & Rhodes 2000;Rhodes et al 2001Rhodes et al , 2003.…”

“…Exposure to faces biases subsequent perceptions of novel faces by causing faces similar to those initially viewed to appear more normal than they would otherwise be perceived (Leopold et al 2001;Rhodes et al 2001Rhodes et al , 2003Rhodes et al , 2004Webster et al 2004;Leopold et al 2005). For example, adaptation to faces with contracted features causes novel faces with contracted features to be perceived as more normal than prior to this exposure (Rhodes et al 2003;Rhodes et al 2004).…”

“…Adaptation from exposure to faces also influences attractiveness judgments potentially due to the positive association between perceived normality and attractiveness (Halberstadt & Rhodes 2000;Rhodes et al 2001Rhodes et al , 2003. Visual after-effects are thought to reflect changes in the responses of neural mechanisms underlying face processing (Leopold et al 2001;Rhodes et al 2003Rhodes et al , 2004Webster et al 2004;Leopold et al 2005;Moradi et al 2005) and cannot be attributed to retinal (i.e. low level) adaptations, as the aftereffects are robust to differences in the retinal location and size of faces at exposure and post-exposure testing (Leopold et al 2001;Rhodes et al 2003Rhodes et al , 2004Leopold et al 2005) and are disrupted by binocular suppression during exposure (Moradi et al 2005).…”

Higher-level mechanisms detect facial symmetry

“…The use of such mechanisms in other aspects of face perception is characterized by superior performance on faces than other patterns, which share low-level properties but do not fully engage these mechanisms. In particular, performance is better on faces than either inverted (upside down) faces (Yin 1969;Moscovitch et al 1997;Murray et al 2000;Rossion & Gauthier 2002;Rhodes et al 2004) or contrast-reversed faces (Galper 1970;Kemp et al 1990;Lewis & Johnston 1997;George et al 1999;Hole et al 1999;Ricciardelli et al 2000). Therefore, if specialized, higher-level mechanisms contribute to the perception of facial symmetry, then symmetry detection should be better for faces than inverted or contrast-reversed faces.…”

Adolescents’ preferences for sexual dimorphism are influenced by relative exposure to male and female faces

“…Visual adaptation to faces manipulated to adjust the spacing of the facial features can lead to subsequent, similar faces being judged as more normal and attractive (Cooper & Maurer, 2008;DeBruine, Jones, Unger, Little, & Feinberg, 2007;Little, DeBruine, & Jones, 2005;Rhodes, Jeffery, Watson, Clifford, & Nakayama, 2003;Rhodes, Jeffery, Watson, Jaquet, Winkler, & Clifford, 2004).…”