The influence of body composition on social judgements

  • Xue Lei

Student thesis: Doctoral Thesis (PhD)


Body Mass Index (BMI; weight scaled by squared height) is a crucial determinant of
physical attractiveness, potentially because BMI signals mate value. Yet, BMI does not
contain information about body composition, namely fat and muscle, which might be a better
indication of mate value. The current thesis explored the potential influence of body
composition on attractiveness and other social judgements.

Study 1 investigated the influence of facial correlates of body composition on
perceived male facial masculinity. Facial correlates of muscle consistently enhanced facial
masculinity, whereas facial correlates of fat increased masculinity perception in underweight
to normal-weight men only.

Study 2 investigated women’s preferences for facial correlates of body composition in
short- and long-term relationships. Women have stronger preferences for facial correlates of
muscle in short- compared to long-term relationships, while no discrepancy was observed in
preferences for facial correlates of fat.

Study 3 investigated how body composition influences health and kindness
judgements from male faces. Perceived health increased with increasing fat and muscle from
underweight to normal-weight men but decreased with further increases in fat and muscle.
Increase in facial correlates of muscle dramatically diminished perceived kindness, but facial
correlates of fat showed a slight detrimental impact on perceived kindness.

Study 4 investigated whether men and women have accurate perceptions of opposite-
sex preferences for body shape. Women exaggerated the thinness that men prefer; men
exaggerated the heaviness and muscularity that women prefer. Moreover, these
misperceptions were larger for short- compared to long-term relationships.

The thesis demonstrates the distinct effects of fat and muscle on social judgements
and reveals that men and women misperceive opposite-sex preferences. These findings point
out the importance of distinguishing body composition of studies of body size.
Date of Award31 Jul 2020
Original languageEnglish
Awarding Institution
  • University of St Andrews
SupervisorDavid Ian Perrett (Supervisor)

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