Under the sun: adaptation effects to changes in facial complexion

Abstract

Background: Many Western people enjoy sunshine, and through the sun's stimulated increase in melanin, the skin tone or skin complexion will darken (and lighten again during winter). Although the initial salience of such a new look is remarkable - especially in the face - we seem to adapt to this new look relatively quickly. Research on face adaptation in general repeatedly showed that the inspection of manipulated versions of faces (so-called adaptor faces) leads to a change of the perception of subsequently presented faces. The present study investigates face adaptation to very natural changes in faces such as changes in complexion.

Methods: During the adaptation phase in the present study, participants saw faces with either strongly increased or decreased complexion. After a pause of 5 min, participants had to identify the veridical (non-manipulated) face out of two faces (a face slightly manipulated in complexion combined with the non-manipulated face) during a test phase.

Results: Results show strong adaptation effects to decreased complexion intensities.

Discussion: It seems that we are updating our facial representations in memory quite quickly (i.e., optimizing our processing through adaptation) and seem to sustain those new representations over a certain timespan (at least 5 min). Our results demonstrate that changes in complexion draw our attention for deeper analysis (at least with decreased complexion). However, it loses its informative quality quickly via fast and relatively sustainable adaptation.

Keywords: Complexion; Face adaptation; Face memory; Face perception; Face recognition; Skin color.

Fig. 1

Examples for the three transfer levels (pictorial, structure, & cross-identity), similar to Mueller et al. [21, 22] (images are just examples and not used within the study; they are taken from https://commons.wikimedia.org under CC BY-SA 3.0 license)

Fig. 2

Example for the different complexion intensities ranging from -75% to + 75%. The non-manipulated image (0%) was used as the original picture (adaptation, test phase), extreme intensities (-75%, + 75%) were used for the adaptation phase, and middle intensities (-25%, + 25%) in combination with the original picture (0%) for the test phase. (Note that these images were not used in the original study but are displayed here for illustrative purposes only; the base image is taken from https://commons.wikimedia.org under CC BY-SA 3.0 license—accordingly, our transformed versions will also be available via CC BY-SA 3.0 ShareAlike license)

Fig. 3

Results of the two experimental phases testing the actually perceived differences between brightness and complexion manipulated stimuli. Asterisks indicate statistical significance based on t-tests, **** p < 0.0001, ** p < 0.01

Fig. 4

Schematic depiction of the trial procedure for the adaptation and test phase

Fig. 5

Illustration of the average selection (mean complexion intensity in % of the selected test stimulus) for the three adaptation conditions (MINUS EXTREME, ORIGINAL, PLUS EXTREME) and the three transfer levels (pictorial, structural, cross-identity). Error bars represent ± 1 standard error of the mean