Transcript 1. Attractiveness & health

Revision lecture 2006
Revision lecture outline
1. Attractiveness & health
2. Self-resemblance as a cue of kinship
3. Hormone-mediated face preferences (cyclic
shifts, pregnancy)
4. Condition-dependent face preferences
1. Attractiveness & health
Evolutionary Advantage account of attractiveness
Proposes that attractiveness judgments reflect adaptations that
promote choice of healthy partners (Thornhill & Gangestad, 1999)
i.e. facial attractiveness signals aspects of health (e.g. fertility, low
number of past health problems, ‘healthy’ genetic profile)
BUT - many researchers have challenged this proposal, noting
that there is little evidence to support this view (e.g. Enquist et al.
2002; Kalick et al. 1999; Valentine et al. 2004)
While early studies of the link between attractiveness and actual
health were not encouraging, more recent studies (with improved
measures of health) present a different picture
1. Attractiveness & health
Kalick et al. (1999)
Tested for a positive correlation between incidence of past health
problems (assessed from medical records) and attractiveness
No relationship observed
BUT - some problems with this study
1.
Interpreting null findings is typically problematic
2.
Face stimuli were low resolution B&W photographs (and some later
studies suggest skin quality may play important role in attractivenesshealth relationship, e.g. Roberts et al.)
3.
Subsequent studies with same image-set found relationships between
some attractive facial cues (e.g. averageness) and health measure
1. Attractiveness & fertility
Law Smith et al. 2006
High levels of oestrogen and progesterone are associated with
fertility among women and are positively related to women’s facial
attractiveness
Penton-Voak et al. 2003
Low waist-hip ratio is associated with fertility among women and is
associated with attractive facial appearance
Both findings support the view that attractiveness in women
signals reproductive health
1. Attractiveness & fertility
Roberts et al. 2004
Late follicular phase of menstrual cycle (i.e. around ovulation) is
most fertile phase
Women’s faces more attractive around ovulation than at other
times
Soler et al. 2003
Facial attractiveness in men is associated with good semen
quality (i.e. higher sperm count and better sperm mobility)
Both findings support link between attractiveness and fertility
1. Attractiveness & ‘good genes’
Roberts et al. 2005
Heterozygosity at the MHC complex (genes that code for
immunity to infectious diseases) associated with strong immune
system
Heterozygotes judged more attractive than homozygotes
Heterozygotes have healthier-looking facial skin than
homozygotes
Although Thornhill et al. (2003) found no link between MHC
heterozygosity and men’s facial attractiveness, they did not
control for age of men or ethnicity
1. Attractiveness & health
Conclusions
Although there is little evidence that facial attractiveness is
associated with (low) frequency of past health problems,
recent findings for links between attractiveness and more
objective/rigorous measures of fertility (e.g. measured
hormone levels, semen quality) and measures of immune
system strength (MHC heterozygosity) present compelling
evidence that facial attractiveness is a cue to various
aspects of health
2. Self-resemblance as a cue of
kinship
Two theories predict that self-resemblance will
influence attitudes to faces:
1.
Inclusive fitness theory: By helping kin you help your genes
pass onto subsequent generations
2.
Inbreeding avoidance: By avoiding sex with kin you prevent
deleterious effects of inbreeding on offspring
2. Self-resemblance as a cue of
kinship
Trusting (DeBruine, 2002)
Tested for effects of self-resemblance of other same-sex players
in an economic ‘trust’ game
People more likely to behave in trusting fashion towards selfresembling players than other-resembling players
Supports key prediction of inclusive fitness theory (trust kin more
than non-kin)
2. Self-resemblance as a cue of
kinship
Attractiveness in own- and other-sex faces
(DeBruine, 2004)
Tested for effects of self-resemblance on preferences for own- and
other-sex faces
Self-resemblance increased attractiveness of own-sex faces
(promoting affiliation with own-sex kin)
Self-resemblance did not increase attractiveness of other-sex
faces to the same extent (reducing likelihood of inbreeding)
2. Self-resemblance as a cue of
kinship
‘Trustworthy not lustworthy’ (DeBruine, 2005)
Previous findings suggested that self-resemblance in other-sex
faces increases trusting but not attractiveness
Self-resembling other-sex faces are 1) perceived as trustworthy,
2) unattractive for short-term relationships (e.g. one-night stands)
and 3) ‘neutral’ in terms of attractiveness for long-term
relationships
Again, suggests that self-resemblance is a cue of kinship - trust
kin but don’t sleep with them!
2. Self-resemblance as a cue of
kinship
Children’s faces (DeBruine, 2004)
DeBruine found self-resemblance increased positive attitudes for
judgments of children’s faces (again, positive attitudes to kin)
Children’s faces are obviously not potential mates, so findings
consistent with claim that self-resemblance preferred in faces of
individuals who are not potential mates (or when faces judged out
with mating context)
Various studies by Platek found the above effect more
pronounced in men than women (no sex difference in DeBruine)
2. Self-resemblance as a cue of
kinship
Attitudes to self-resemblance
Increased preference for self-resembling faces when raised
progesterone level prepares body for pregnancy (DeBruine,
Jones & Perrett, 2005)
That effect is most pronounced for female faces suggests the
effect reflects increased preference for sources of support and
care than mechanism for avoiding inbreeding
Indeed, change in preference for self-similar faces related to
progesterone level NOT conception risk
2. Self-resemblance as a cue of
kinship
Conclusions
People appear to use self-resemblance as a cue of kinship when judging others
Consistent with inclusive fitness theory, self-resemblance increases positive
attitudes when ‘target’ is not a potential mate (e.g. children and same-sex
individuals) or when other-sex faces are judged out with mating context (e.g.
increases perceived trustworthiness of other-sex faces)
Consistent with inbreeding avoidance, self-resemblance decreases attractiveness of
potential mates when judged for an explicitly sexual relationship (e.g. a one night
stand)
That attitudes to self-resemblance are sensitive to the context (I.e. the ‘question’
asked) and face-type (child, own-sex, other-sex) in these ways supports the view
that self-resemblance is a cue of kinship and are difficult to explain in terms of
attitudes to familiar stimuli
3. Hormone-mediated attraction
Masculinity preferences (Penton-Voak et al 1999)
Cost to preferring masculine men:
Anti-social personality traits + low investment (Perrett et al. 1998)
Benefit to preferring masculine men (handicap hypothesis):
Good genes for offspring health (Thornhill & Gangestad, 1999)
Women may maximize the benefits of their mate preferences by
preferring feminine men generally but being more attracted to
masculine men around ovulation (when most fertile) - particularly
pronounced when partnered women judge unfamiliar men for
short-term relationship (i.e. possible EPC)
Similar effects seen for voice preferences (Feinberg et al. 2006)
3. Hormone-mediated attraction
Attitudes to romantic partner and cycle phase
If cyclic shifts in women’s preferences for masculine men reflect
an adaptation for securing good genes for immunocompetence
within long-term relationship with feminine, ‘caring sharing’ man,
then attitudes to long-term partner should also change around
ovulation
Increased incidence of sexual fantasy about men other than
primary partner around ovulation (Gangestad et al. 2002)
Reduced commitment to romantic partner around ovulation, but
no change in happiness with relationship (Jones et al. 2005)
3. Hormone-mediated attraction
Attitudes to self-resemblance
Increased preference for self-resembling faces when raised
progesterone level prepares body for pregnancy (DeBruine,
Jones & Perrett, 2005)
That effect is most pronounced for female faces suggests the
effect reflects increased preference for sources of support and
care than mechanism for avoiding inbreeding
Indeed, change in preference for self-similar faces related to
progesterone level NOT conception risk
3. Hormone-mediated attraction
Contagion avoidance (Jones et al. 2005)
Increased aversions to possible sources of contagion (e.g. meat)
observed during early pregnancy thought to reflect mechanism for
protecting developing fetus and mum-to-be
Increased aversion to unhealthy faces during pregnancy, luteal
phase of menstrual cycle and following oral contraceptive use (all
high progesterone conditions)
Increased aversion to unhealthy faces also associated with raised
progesterone during menstrual cycle
3. Hormone-mediated attraction
Conclusions
Although we tend to think of people having ‘types’ that they find
attractive (i.e. tend to think of preferences as stable within an
individual), these findings show that changes in hormone levels
are associated with predictable changes in face preferences
Although it is now well established that face preferences change
systematically during the menstrual cycle, the hormonal
mechanisms that cause this remain poorly understood
Most previous studies have emphasized the likely importance of
changes in progesterone level, but other hormones are probably
also important (e.g. testosterone level)
4. Condition-dependence
Stickleback (Bakker et al. 1999)
Male stickleback signal good health via red throat patch
and males with red throat patches are preferred
Heavy female stickleback are healthier than lighter
stickleback and have the strongest preferences for
healthy males
Adaptive behavior if healthy females are better able to
compete for healthiest mates
4. Condition-dependence
Condition-dependent health preferences among
women (Jones et al. 2005)
Low waist-hip ratio (WHR) signals health in women
- Women with low WHR have stronger preferences for apparent
health in men’s (but not women’s) faces than women with higher
WHRs do
- Low stress and anxiety among women also associated with
increased preference for male apparent health
These findings are analogous to condition-dependent preferences
seen in stickleback
4. Condition-dependence
Masculinity preferences
Cost to preferring masculine men as long-term partners: Antisocial personality traits + low investment (Perrett et al. 1998)
Women with high SRA (Little et al. 2001), high other-rated facial
attractiveness or low WHR (Penton-Voak et al. 2003) have
stronger preferences for masculine men as long-term partners
than do relatively unattractive women
Attractive women better able to offset possible costs of choosing a
masculine long-term partner?
4. Condition-dependence
Different from matching hypothesis
Matching hypothesis suggests that people take into
account their own attractiveness when choosing a
romantic partner ONLY when there is a possibility of
being rejected (i.e. not on face preference tests)
However, findings for condition-dependent face
preferences show that own attractiveness can modulate
face preferences even when there is no possibility of
rejection
Good luck in the exam