Facial symmetry and judgements of apparent health: Support for a “good genes” explanation of the attractiveness–symmetry relationship

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Abstract

The “good genes” explanation of attractiveness posits that mate preferences favour healthy individuals due to direct and indirect benefits associated with the selection of a healthy mate. Consequently, attractiveness judgements are likely to reflect judgements of apparent health. One physical characteristic that may inform health judgements is fluctuating asymmetry as it may act as a visual marker for genetic quality and developmental stability. Consistent with these suggestions, a number of studies have found relationships between facial symmetry and facial attractiveness. In Study 1, the interplay between facial symmetry, attractiveness, and judgements of apparent health was explored within a partial correlation design. Findings suggest that the attractiveness–symmetry relationship is mediated by a link between judgements of apparent health and facial symmetry. In Study 2, an opposite-sex bias in sensitivity to facial symmetry was observed when judging health. Thus, perceptual analysis of symmetry may be an adaptation facilitating discrimination between potential mates on the basis of apparent health. The findings of both studies are consistent with a “good genes” explanation of the attractiveness–symmetry relationship and problematic for the claim that symmetry is attractive as a by-product of the ease with which the visual recognition system processes symmetric stimuli.

Introduction

The “good genes” account of attractiveness posits that mate preferences may have evolved to favour healthy individuals due to direct and indirect benefits associated with the selection of a healthy mate Andersson, 1994, Gangestad & Simpson, 2000, Miller & Todd, 1998, Thornhill & Gangestad, 1993, Thornhill & Gangestad, 1999. If this is the case, attractiveness judgements are likely to reflect judgements of health (Grammer & Thornhill, 1994). It has also been suggested that fluctuating asymmetry is a visual marker for genetic quality and developmental stability—the ability to maintain good health in the face of environmental insults Gangestad & Simpson, 2000, Møller & Swaddle, 1997, Møller & Thornhill, 1997, Thornhill & Møller, 1997.

Consistent with these suggestions, a number of studies have found that symmetry in real faces is associated with judgements of facial attractiveness Grammer & Thornhill, 1994, Hume & Montgomerie, 2001, Mealy et al., 1999, Rhodes et al., 1998, Rhodes et al., 1999, Scheib et al., 1999. Moreover, preferences for faces that have been “morphed” to be more symmetrical have also been reported Perrett et al., 1999, Rhodes et al., 1999, Rhodes et al., 2001. Consequently, many researchers have concluded that symmetry is a visual cue to facial attractiveness. For some, however, the link remains in debate (e.g., Penton-Voak et al., 2001, Scheib et al., 1999, Swaddle & Cuthill, 1995).

Both Grammer and Thornhill (1994) and Penton-Voak et al. (2001) found that judgements of health were related to symmetry in male faces. In line with these findings, Rhodes, Zebrowitz, et al. (2001) reported associations between rated facial symmetry and judgements of apparent health for both male and female faces. The apparent health of symmetric faces could, however, reflect an “attractiveness halo” where positive attributes (e.g., extraversion, stability, and good health) are ascribed to good looking, symmetrical individuals (Penton-Voak et al., 2001). Indeed, there is some evidence that apparent good health may simply be a stereotype associated with attractive individuals (Kalick, Zebrowitz, Langlois, & Johnson, 1998). If the relationship between symmetry and judgements of apparent health was mediated by an attractiveness halo effect, it would pose difficulties for a “good genes” explanation of the attractiveness–symmetry relationship (see Feingold, 1992, Langlois et al., 2000 for meta-analytic reviews of research on attractiveness halo effects).

It has been reported that manipulating digital face images so as to increase symmetry engenders an increase in ratings of apparent health (Rhodes, Zebrowitz, et al., 2001). This finding suggests that symmetry is a cue to judgements of health. If the processing of symmetry by the perceptual system is an adaptation facilitating discrimination between potential mates on the basis of apparent health (Møller & Thornhill, 1998), a strong adaptationist position might predict an opposite-sex bias in sensitivity to facial symmetry. In contrast, no such bias is predicted by accounts claiming that symmetry is found attractive as a by-product of the ease with which the recognition system can process symmetric stimuli (e.g., Bradbury & Vehrencamp, 1998, Enquist & Arak, 1998, Enquist & Ghirlanda, 1998). Consistent with the strong adaptationist position, Little, Burt, Penton-Voak, and Perrett (2001) report that manipulations of symmetry have a greater impact on attractiveness ratings of opposite-sex faces than ratings of own-sex faces. As yet, there have been no reported tests for such a bias when judging apparent health.

Two studies are reported here that explore predictions about the relationship between facial symmetry and judgements of apparent health that arise from the “good genes” explanation of attractiveness.

Section snippets

Study 1

In Study 1, the interplay between measured facial symmetry, judgements of apparent health, and judgements of attractiveness was explored within a partial correlation design. The “good genes” explanation of attractiveness predicts that, rather than being the result of an attractiveness halo, the association between symmetry and judgements of apparent health mediates the attractiveness–symmetry relationship. Consequently, if the association between facial symmetry and apparent health judgements

Participants

Ten male (21–26 years old) and 10 female (20–28 years old) participants took part in Study 1. All participants reported normal or corrected-to-normal vision and were naı̈ve to the purpose of the experiment.

Stimuli

Full-face photographs of 30 males and 30 females (20–30 years of age, all undergraduate students at the University of St. Andrews) were used. Each full-colour photo was taken with a digital camera (resolution set at 1200×1000 pixels) and under standardised diffuse lighting conditions.

Interrater reliability

Interrater agreement for ratings of both attractiveness (Cronbach's α=.83) and apparent health (Cronbach's α=.92) were higher than .8 and rating was therefore taken to be reliable (Bohrnstedt, 1970). Ratings from male and female participants were combined for subsequent analyses.

Descriptive statistics

Summary statistics of all measures are shown in Table 1. Table 1 also shows that for each measure the distribution of scores did not differ significantly from a normal distribution, and that the most extreme value for

Discussion

The simple linear correlations found in Study 1 show that high attractiveness is attributed to individuals whose faces are symmetrical. This finding is consistent with other studies Grammer & Thornhill, 1994, Hume & Montgomerie, 2001, Mealy et al., 1999, Perrett et al., 1999, Rhodes et al., 1999, Rhodes et al., 1998, Rhodes et al., 2001, Scheib et al., 1999. The simple linear correlations also show that good health is attributed to individuals whose faces are symmetrical which, again, is

Study 2

Study 2 explored the impact of manipulations of facial symmetry on perceived health. A strong adaptationist position would predict an increased sensitivity to facial symmetry when judging the apparent health of opposite-sex face images. Apparent health ratings of images of normal faces were compared with ratings of images of faces in which symmetry was increased by digitally “morphing” the image.

Participants

Thirteen male (20–30 years old) and 13 female (20–30 years old) participants took part in Study 2. All participants reported normal or corrected-to-normal vision and were naı̈ve to the purpose of the experiment. None of the participants in Study 2 had taken part in Study 1.

Design

A within-subjects design was used with factors facial symmetry (two levels: normal, more symmetrical) and sex of face (two levels: own-sex, opposite-sex).

Stimuli

Male and female faces (Caucasian, 15 male and 15 female, ages 20–30

Results

Mean ratings of apparent health for own-sex symmetrical, opposite-sex symmetrical, own-sex normal, and opposite-sex normal faces were calculated for each participant and used in subsequent analyses. As the distribution of ratings was not significantly different from a normal distribution (Table 4), parametric tests were used for subsequent analyses.

A within-participants analysis of variance (ANOVA) showed a significant main effect for facial symmetry [F(1,103)=114.6, P<.001] and no main effect

Discussion

The observed main effect for facial symmetry shows that increasing symmetry improved ratings of apparent health. Though this link between facial symmetry and apparent health occurred when rating both own-and opposite-sex faces, analyses indicated an opposite-sex bias in sensitivity to facial symmetry when judging health (Fig. 3). This finding is consistent with the suggestion that the perceptual analysis of facial symmetry may be an adaptation facilitating discrimination between potential mates

General discussion

The findings of Study 1 indicate that the relationship between facial symmetry and attractiveness is mediated by judgements of apparent health. This is evidence against the proposition that the attractiveness of symmetry is simply a by-product of the ease with which the recognition system can process symmetric stimuli (e.g., Bradbury & Vehrencamp, 1998, Enquist & Arak, 1998, Enquist & Ghirlanda, 1998). It may be that the undergraduate population, sampled in order to create the item set in Study

References (33)

  • M Enquist et al.
  • M Enquist et al.

    Evolutionary biology—the secrets of faces

    Nature

    (1998)
  • C.S Evans et al.

    Detection of bilateral symmetry in complex biological images

    Perception

    (2000)
  • A Feingold

    Good-looking people are not what we think

    Psychological Bulletin

    (1992)
  • S.W Gangestad et al.

    The evolution of human mating: trade-offs and strategic pluralism

    Behavioral and Brain Sciences

    (2000)
  • K Grammer et al.

    Human (Homo sapiens) facial attractiveness and sexual selection: the role of symmetry and averageness

    Journal of Comparative Psychology

    (1994)
  • Cited by (0)

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