PSYC 3100 Lecture Notes - Lecture 18: Sperm Competition, Enclosed Religious Orders, Abusive Power And Control
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Outline of Lecture 18 Conflict 2
Note: this lecture will be disturbing to some, as it deals with conflict (and abuse) within
1. Sperm Competition
- Responses to cues of sperm competition: prevention, more sperm, reduced parenting
-sexual selection and competition for mates does not always end at mating
-if multiple males mate with a female, only one sperm will fertilize each egg
-sperm competition: increasing the likelihood that one's sperm will fertilize the eggs
-number of ways to do this: put out more sperm, invest more in sperm production
Investment in Sperm
-nontrivial costs of sperm production, incl. “depletion”
-across species: rates of polyandry (risk of sperm competition) correlate with
testes size (relative to body size)
-orangutangs, gorillas: keep females to themselves (alpha), small testes
-chimps: females mate with many guys, testes are huge compared.
-males: less polyandry than chimps, but more than gorillas. Big testes
Male Responses to Cues of Sperm Competitions
-preventative tactics: mate guarding & coercion
-sperm competition tactics: mate more often, release more sperm per mating
(“overwhelming”), remove competitors' sperm
-differential parental investment: reduced investment in presence of cues of
do human males do this?
-the more time male spends with female partner, the less sperm he
ejaculates. Fewer cues of sperm competition with more time spent
Sperm Competition and Arousal
hypothesis: cues of sperm competition lead to higher arousal (I.e, a need for more
sperm relatively soon)
non-humans: let a male mate with a female after observing her mate with another
male, measure sperm. Male will pump out more sperm after watching a male mate
with a female before he does.
Humans: measure sperm responses to images involving sperm competition (i.e.
more than one or one male with females)
2. Strategies for reducing infidelity
Costs of Infidelity: partner infidelity is harmful to one's RS
-cuckoldry (males only)
-diverting resources (more a problem for females)
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