PSY 343 Lecture Notes - Lecture 2: Incest, Parental Investment, Prosocial Behavior
1. Personality Psychology Unit 2: Personality Development
Evolutionary Psychology
1. Much of human behavior reflects psychological structures and mechanisms that evolved because
they helped us adapt to environmental challenges over the course of human evolution. For now,
let’s just look at the period since the genus homo emerged about 1.5 million years ago – a period
termed the environment of evolutionary adaptiveness [EEA]
2. Buss and Larsen suggest that evolutionary psychology offers insight into personality in three main
areas: ALL people – human nature, SOME people – sex differences, & NO OTHER people –
individual differences.
3. I) Some General Evolutionary Theory Issues
1. A) Darwin and evolution by natural selection – the importance of variation and scarcity.
1. 1. survival selection (with examples, please)
2. 2. sexual selection (with examples, please)
1. a) intrasexual competition
2. b) intersexual selection
2. B) Modern evolutionary biology
1. Inclusive fitness theory
1. shift from the individual to the gene as the focus of evolution
2. differential gene reproduction
3. and some illustrative examples...............
2. Finally, evolutionary psychologists like Buss and Larsen hold three key, interconnected
assumptions:
1. a) domain specificity
2. b) functionality
3. c) numerousness – Buss’s eight reproductive challenges
1. successful intrasexual competition
2. mate selection
3. successful conception
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4. mate retention
5. reciprocal dyadic alliance formation
6. coalition building and maintenance
7. parental care & socialization
8. extraparental kin investment
4. II) Sex Differences
1. A) Mate Selection – both sexes should be adapted to seek mates who will help them pass on
their genes. However, the characteristics that males have that make them good choices for
mating may not be the same as what make women good reproductive partners.
1. While the “official version of the story” seems potentially sensible and is certainly
consistent with the data Buss and Barnes gathered, consider the following:
1. out of that long list of characteristics they gave participants, earning capacity received
an average ranking of 8.04 from females and 9.92 from males – a statistically significant
sex difference. But should we read this as evidence that what women MOST look for is
earning potential (and, in like manner, men most look for youth and beauty)? That is the
primary narrative that has emerged, but keep in mind that data don’t speak for
themselves. Psychologists interpret data and the same data can be used to “tell
different stories.” We most emphatically are NOT talking “alternative facts” or “fake
science” here. Both stories may be true, but with very different emphases and
implications.
1. By the way, this is a caution to keep in mind when reading gender difference
research. Researchers can enter into their work with unexamined biases. Many,
though of course not all, seemed predisposed to jump on and report the differences
between the sexes while paying scant attention to the usually larger pool of
similarities. And surprise of all surprises, those differences often appear to reinforce
established gender stereotypes.
2. Here are two further things to ponder.
1. Not all the differences we observe in a current population are instances of evolutionary
pressures. If variation in a characteristic cannot be shown to confer adaptive advantage,
then it’s not relevant from an evolutionary point of view. To illustrate, do folks with
blond hair survive and reproduce at higher rates than folks with brown hair? More to
our area of concern, consider what is meant by “beauty” or “physically attractive.”
1. Why does it allegedly matter?
2. How much must be present to matter? Too much, too little, just right?
3. And, most important, what do we mean by “matter”?
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3. Just because a behavior can be shown to be advantageous doesn’t mean it emerged due to
bio-evolutionary factors. To illustrate, in many historical and contemporaneous societies,
mate selection is not conducted by the potential partners but by their parents.
1. On what basis are advantageous selections made?
2. And for the bigger question, are these evolutionary mediated mechanisms?
2. B) Mating Strategies – the primary drive of both sexes is to maximize their reproductive success
but due to their different roles in reproduction, each sex confronts different limitations and is,
therefore, purportedly drawn to a different strategy.
1. Potential complications – If there are within a population roughly as many men as women
playing the Great Reproductive Game, are there any costs to the presumed “promiscuous
male” strategy?
1. Incest
2. Std/sti
3. Childcare/ child learning
4. Uncertainty
5. Competition for access to females
2. From a male’s point of view: the more women he can couple with to impregnate that
maximizes his reproductive success. More couplings he can do, more he can pass on his
genes to next generation. Strategy of quantity
3. From a female’s point of view: strategy of quality- because when they are pregnant they
cannot become pregnant again until they give birth. So they want their reproductions to be
of high quality
3. C) If the Great Reproductive Game involves competition and various costs, are there
evolutionary mechanisms for detecting/dealing with threats to one’s reproductive success?
(This is one aspect of mate retention: how to protect against rivals poaching on your
reproductive territory.)
1. There is a mechanism that we have that detects a threat or rival coming to take our sexual
partner= jealousy
2. Jealousy serves a purpose of a warning signal that someone might take out sexual partner
4. Sexual Differences in Jealousy article:
1. Paternal uncertainty- there is a potential risk to male humans to be uncertain if the
offspring is theirs.
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