Face distortion aftereffects evoked by featureless first-order stimulus configurations

Abstract

After prolonged exposure to a distorted face with expanded or contracted inner features, a subsequently presented normal face appears distorted toward the opposite direction. This phenomenon, termed as face distortion aftereffect (FDAE), is thought to occur as a result of changes in the mechanisms involved in higher order visual processing. However, the extent to which FDAE is mediated by face-specific configural processing is less known. In the present study, we investigated whether similar aftereffects can be induced by stimuli lacking all the typical characteristics of a human face except for its first-order configural properties. We found a significant FDAE after adaptation to a stimulus consisting of three white dots arranged in a triangular fashion and placed in a gray oval. FDAEs occurred also when the adapting and test stimuli differed in size or when the contrast polarity of the adaptor image was changed. However, the inversion of the adapting image as well as the reduction of its contrast abolished the aftereffect entirely. Taken together, our results suggest that higher-level visual areas, which are involved in the processing of facial configurations, mediate the FDAE. Further, while adaptation seems to be largely invariant to contrast polarity, it appears sensitive to orientation and to lower level manipulations that affect the saliency of the inner features.

Keywords: configural processing; contrast polarity; face distortion aftereffect; first-order relations; second-order relations.

Figure 1

Procedures and example stimuli. The flowchart illustrates the adaptor stimuli used in Experiment 1 and one of the three test faces used during the experiments as an example. Adaptor stimuli from top to down: contracted (CONT) and expanded (EXP) white dots. Test stimuli from top to down: −10% (expanded) and +10% (contracted) distorted faces.

Figure 2

Mean ratio of stimuli endorsed as contracted as a function of distortion level (% distorted). Negative and positive distortion levels correspond to expanded and contracted target faces respectively. Results obtained by using contracted (CONT) and expanded (EXP) white dots as adaptor stimuli. The inset illustrates the adaptor stimuli. Data are modeled by a Weibull psychometric function.

Figure 3

Mean ratio of stimuli endorsed as contracted as a function of distortion level (% distorted) when the relative size of adaptor and target was varied. Negative and positive distortion levels correspond to expanded and contracted target faces respectively. Results obtained by using versions of contracted (CONT) and expanded (EXP) white dot adaptors that differed in size from the target stimuli.

Figure 4

Mean ratio of stimuli endorsed as contracted as a function of distortion level (% distorted) when the adaptor images were upside-down. Negative and positive distortion levels correspond to expanded and contracted target faces respectively. Results obtained by using the inverted versions of contracted (CONT) and expanded (EXP) white dots as adaptors.

Figure 5

Mean ratio of stimuli endorsed as contracted as a function of distortion level (% distorted) with adaptors of opposite contrast polarity. Negative and positive distortion levels correspond to expanded and contracted target faces respectively. Results obtained by using white dots on a black oval (White dots CONT and White dots EXP) and black dots on a white oval (Black dots CONT and Black dots EXP).

Figure 6

Mean ratio of stimuli endorsed as contracted as a function of distortion level (% distorted) with low-contrast adaptor features consisting of visual noise. Negative and positive distortion levels correspond to expanded and contracted target faces respectively. Results obtained by using the contracted (CONT) and expanded (EXP) dots consisting of visual noise.