PS4029/30 Perspectives on social attributions Lecture 5

1.Prototype faces (recap) 2.Evolutionary advantage account of attractiveness 3.Facial attractiveness & medical health 4.Facial attractiveness & genetic health 5.Facial attractiveness & fertility Lecture 5: Do attractive faces signal health?

In order to recognise faces, we must have a mental representation of “face” This mental representation is most probably a prototype (see neural network example L3) 1. Prototype faces

Computer graphic methods are used to construct prototype images These are synthetic images with the mean shape, color and texture information from a sample of faces Prototype images can be thought of as visual representations of prototypes of mental representations 1. Prototype faces

++ warp BUILDING PROTOTYPE FACES IN SHAPE AND COLOUR

Evolutionary advantage view of facial attractiveness suggests that attractiveness judgements are psychological adaptations that identify good potential mates Thornhill & Gangestad, 1999 TICS 2. Evolutionary advantage account of attractiveness

Good potential mates will: Have strong immune systems Have healthy genetic profile Be fertile These people should also have attractive faces (Thornhill & Gangestad, 1999) 2. Evolutionary advantage account of attractiveness

Some researchers have noted that the BIGGEST problem for the evolutionary advantage view of attractiveness is that there is no evidence that people with attractive faces are particularly healthy Enquist et al. (2002) 2. Evolutionary advantage account of attractiveness

3 methods have been used to explore this issue Studies of: Past incidence of health problems Indices of genetic health (MHC heterozygosity) Measures of fertility 2. Evolutionary advantage account of attractiveness

Individual’s health during adolescence assigned score from detailed medical records assessed by panel of doctors B&W photographs rated for attractiveness Male faces: No relationship between health score and attractiveness rating Female faces: No relationship between health score and attractiveness rating Facial attractiveness & medical health (Kalick et al., 1998)

Facial attractiveness & genetic health (Roberts et al., 2005) Heterozygosity at major histocompatability complex (MHC) indicates a genetic profile consistent with strong immune system Male faces: males who had heterozygous MHC more attractive than males with homozygous MHC Female faces: Not tested

heterozygous (good immunity) homozygous (poor immunity) VISIBLE SKIN CONDITION AND IMMUNITY TO INFECTION

Facial attractiveness & genetic health (Thornhill et al., 2003) Thornhill et al. found no link between MHC heterozygosity and facial attractiveness is men The men in their study were of diverse ages and ethnicities and this might be why By contrast all particpants in Roberts et al’s MHC study were of the same ethnicity and a narrow age range

Fertile phase of menstrual cycle is the late follicular phase Photographs of women’s faces are more attractive when taken at this time that photograph’s of the same women’s faces taken at other times Facial attractiveness & fertility (Roberts et al. 2004)

A low WHR (curvy body shape) in women is an indicator of reproductive health Women with low WHR also have attractive faces Bodies and faces may be 2 signals of a common underlying quality (‘health’) Facial attractiveness & WHR (Penton-Voak et al. 2003)

Semen quality assessed from samples using WHO guidelines Men whose faces were judged attractive had healthier sperm than men judged relatively unattractive Facial attractiveness & fertility (Soler et al. 2003)

Although little evidence that past health problems predict facial attractiveness, there is evidence that attractive faces signal reproductive and genetic health This supports a key claim of the evolutionary advantage account of facial attractiveness Lecture 5: Key themes

The relationship between facial averageness and attractiveness will be discussed “Are attractive faces only average?” Next week