PSYC 2600 Lecture Notes - Lecture 5: Inclusive Fitness, Infidelity, David Buss

19 views2 pages
25 Jul 2016
of 2
Thursday, July 21st, 2016
PSYC 2600 Evolution
-Evolutionary theory, evolutionary psychology
-Making & testing predictions about personality from evolutionary psychology
Natural Selection & Reproductive Success:
-Natural Selection:
oNaturally occurring variation leads to differences in ability to survive &
reproduce (reproductive success)
Next generation contains more successful variant
oSuccessful variants selected & unsuccessful variants weeded out
oOver time, successful variants come to characterize entire species
oAdaptations: inherited solutions to survival & reproductive problems posed by
hostile forces of nature
Sexual Selection:
-Many mechanisms seemed to threaten survival
oE.g. peacock’s elaborate plumage
-Evolution by sexual selection as solution
oThese traits evolved b/c they contributed to individual’s mating success
oIntrasexual competition: members of same sex compete w/ each other for sexual
access to members of other sex
oIntersexual competition: members of 1 sex choose mate based on their
preferences for particular qualities in that mate
Genes and Inclusive Fitness:
-Discovery of gene as unit of inheritance led to key discovery, that natural selection &
sexual selection are diff forms of same process
oDifferential gene reproduction – reproductive success relative to others
-Inclusive fitness theory (Hamilton, 1964):
oPersonal reproductive success (# of offspring you produce) plus effects you have
on reproduction of your genetic relatives, weighted by genetic relatedness
find more resources at
find more resources at
-Primary products of selection, defined as “reliably developing structure in the organism
which, because it meshes with the recurrent structure of the world, causes the solution to
an adaptive problem”
oAdaptive problem: anything that impedes survival or reproduction
Human Nature:
-Need to belong, helping & altruism, universal emotions
Sex Differences:
-Males & females will be same or similar in all domains where sexes have faced same or
similar adaptive problems
-Males & females will be diff in those domains where sexes recurrently faced diff
adaptive problems
oMen over evolutionary history have risked investing in children who weren’t their
Men should be more jealous in response to cues to sexual infidelity
Women should become more distressed over partner’s emotional infidelity
Shackelford, Buss & Bennett (2002):
-Students (264) completed & faced w/ several forced-choice dilemmas:
oE.g., what would upset you more?
Sexual infidelity, emotional infidelity
oMen, relative to women, find it more difficult to forgive sexual infidelity than
emotional infidelity
oMen, relative to women, more likely to terminate current relationship following
partner’s sexual infidelity than emotional infidelity
Desire for Sexual Variety:
-Clark & Hatfield (1989):
oMembers of the sex that invest less in offspring predicted to be less discriminating
in their selection of mates & more inclined to seek out multiple mates
find more resources at
find more resources at
-Evolutionary theory predicts men more inclined to seek multiple mates to increase their
reproductive success
The Big Five and Evolutionarily-Relevant Adaptive Problems:
-Big Five personality traits as clusters of key features of “adaptive landscape” of other ppl
-Human have evolved “difference-detecting mechanism” designed to notice & remember
individual differences that have most relevance for solving social adaptive problems
Limitations of Evolutionary Psychology:
-Evolution has large time span:
oCan’t go back in time
oPrecise selective forces?
-Modern conditions “≠” ancestral conditions
find more resources at
find more resources at