4 - ENVIRONMENTAL EFFECTS ON SEXUAL BEHAVIOUR Flashcards
experimental evidence of learning on sexual behaviour in rats
- instinctive behaviour is already influenced by learning
- mixed sex groups
- iso-sex groups (one sex) = kind of response but less competent at performing rat specific sexual behaviour
- isolation rearing = no response = incompetent
- no adults present during rearing = no imitation learning (if innate then should adopt regardless of mother - not the case)
- prepubertal learning depends on social interaction with opposite sex
- attracted to siblings? no! - evidence of more attracted to females who grew up in another nest
definition of the westermarck effect
two animals (or human siblings) are less likely to find each other sexually attractive is they have been raised together than if they have been raised apart
westermarck effect
bevc & silverman (1993)
- intimacy variables did not relate to incestuous behaviour
- separation for more 1 year during first 6 years = sig related to consummatory sexual activities = proves effect
- opposite effect for non consummatory
- early association = barrier to mature sexual activities = reduce pro creative potential - but doesn’t reduce sexual interest
- more mature activities in non biological siblings
westermarck effect
shepher (1971,1983)
marriages rarely occurred in persons raised in communes in the same peer group for the first six years of life
but maintained platonic friendships
westermarck effect
mccabe (1983)
found higher incidence of divorce and fewer children between cousins raised together in lebanese villages
westermarck effect
bevc & silverman (2000)
- separation during childhood associated with later acts of potentially pro creative nature
- both sexual groups report more nudity and physical contact in childhood than non sexual groups (opposite to hypothesis)
- revised westermarck effect = organism selectively responds to stimuli specifically mediating facilitation and inhibition of genital intercourse
westermarck effect
bearman & brickner (2002)
- males with female twin more likely to report same sex attraction
- support socialisation model at an individual level
- families with OS twin and no older brother = twice as high probability of same sex attraction in males
- due to socialisation effects - gender norms from not having an older brother
- half in females
environmental effects without learning
postnatal: gender-specific maternal behaviour
- rat mothers lick genital region of newborn pups (clean + stimulate urination)
- male pups licked more (due to specific smell caused by more androgens)
- male pups licked same amount as females (mother prevented from smelling) = reduced male typical sexual behaviour as adults (less androgens)
- by females licking more = nothing changes - the testes produce androgens so doesn’t affect females
- licking increases androgen levels in newborn males = promotes male typical brain development = more androgens = more estrogen = larger SDN-POA (aromatisation)
environmental effects without learning
prenatal: maternal stress effect
- ‘stressing’ pregnant rats during a critical period causes their male offspring to show reduced male-typical behaviour as adults
- maternal stress hormones disrupt peak androgen levels in male embryos
- levels peak before critical brain development
- less androgens = less estrogen = smaller SDN-POA
- stressing by putting in bright light (don’t like day time)
- question must talk about hormones (either stress or sex)
environmental effects without learning
prenatal: uterine contiguity effect
- female rats that develop in the uterus next to male sibling (downstream) = increased male typical behaviour
- larger SDN-POA
- share a blood supply with siblings - hormones travel in the blood
- less likely to show lordosis
what are the three examples of environmental effects on behaviour
(3 things)
1 gender specific licking
2 maternal stress effect
3 uterine contiguity effect
what is the speculated role of the SDN-POA?
- inhibit female-typical sexual behaviour
- female sexual behaviour ‘default’
- small SDN-POA = default behaviour not inhibited
- large SDN-POA = can inhibit default behaviour / trigger alternative behaviour (male sexual behaviour)
- larger the SDN-POA, the higher chance of inhibiting default
- data is inline with this interpretation but not concrete
what is the effect of mix sex rearing on behaviour?
- social learning probably has no direct effect on sexy hormone levels
- more likely animals practice and reinforce instinctive behaviours during play
information:
genes and environment determine pre and post natal sex hormone levels
sex hormones modulate sex-specific brain development
having a particular brain structure makes animals more likely (still need practice) to exhibit sex-specific behaviour
must be practiced during adolescence in order to be performed properly in adulthood
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