Evolutionary
Psychology
Lecture 1
Lisa DeBruine
[email protected]
01224 27-2243
Room S7 William Guild Building
course website - http://facelab.org/evpsych
What can evolutionary theory
tell us about behaviour?
The logic of Natural Selection
• Organisms produce more offspring than
can possibly be supported by the
environment
• There is variation in how well-suited
individuals are to their environment and this
affects their chances of survival and
reproduction
• Some of this variation is heritable
Currently Adaptive Behaviours
• Help generate and evaluate hypotheses
• Recognize different types of behaviours
• Currently adaptive behaviours
• Previously adaptive behaviours
• By-products of adaptive behaviours
Previously Adaptive Behaviours
Previously Adaptive Behaviours
The desire to overeat fats and sweets when they
are available was probably adaptive when these
foods were rare and the main consequence was to
motivate people to eat fresh fruit.
The inclination to delay childbearing and have
fewer children when the environment is highly
competitive and survivorship is high was probably
adaptive up to a point. Now, research indicates
that some modern women have followed this trend
to a maladaptive extreme (Low, 2002).
By-products of Adaptive Behaviours
Some behaviours can be explained as by-products or
“spandrels” (Gould & Lewontin, 1979).
Criticisms of Evolutionary Psychology
• Evolutionary hypotheses are always just-so
stories.
• Evolutionary hypotheses are unfalsefiable.
• Evolutionary psychology is intrinsically
racist, classist, sexist, homophobic, etc.
• Explaining human behaviour using
evolutionary theory is too reductionist.
Many behaviours are obviously not a result of natural
selection for that specific behaviour, such as the
ability to read or to ride a bike.
Areas in which Researchers Use an
Evolutionary Approach to Behaviour
2D:4D and Testosterone
• Prenatal T influences the brain
and (maybe) 2nd to 4th digit
ratio.
• Medicine
• Biology
• Low 2D:4D indicates high
prenatal T levels.
• Anthropology
• Experimental Economics
• Psychology
• Neuroscience
Cross-cultural diversity in use of spices
• Low 2D:4D in men is correlated
with musical ability, athletic
ability, heterosexuality, and many
other traits (Manning, 2002).
Cross-cultural diversity in use of spices
Use of spices varies with
climate; data from 32 countries.
Norway is the coldest and
Thailand is the hottest.
(Billing & Sherman, 1998)
(Billing & Sherman, 1998)
Who do you think the baby is most similar to?
Prisoner’s Dilemma
Player 2
cooperate
Player 1
defect
cooperate
3
3
0
5
defect
5
0
1
1
Mother
Father
Other
14
17
29
20
57
54
53
47
29
29
18
33
Respondent:
Mother
Father
Mo’s relative
Fa’s relative
(Daly & Wilson, 1982)
Who would you help?
Genetic Compatibility
Women who were not using oral contraceptives
rated the odours of MHC-dissimilar men (sharing 0
or 1 allele) to be more pleasant than the odours of
MHC-similar men (sharing 3 or 4 alleles).
Women who
were using the
pill showed the
opposite pattern.
Pleasantness ratings of male odours by females
MHC-similar
7
MHC-dissimilar
6
5
4
3
(Wedekind
et al.,1995)
2
1
0
(Burnstein et al., 1994)
Female Preferences for Masculinity
over the Menstrual Cycle
Mean feminization prefered
low conception risk
high conception risk
Non-Pill Users
reciprocity
mate
choice
15%
kin
selection
altruism
costly
signaling
cheater
detection
resources
kin
recognition
perception
10%
sex
differences
5%
0%
short term context
long term context
mating
Pill Users
parentoffspring
conflict
offspring