Sexual Behaviours Flashcards
Determining sex
Primary characteristics - diff genitalia
Secondary characteristics - body hair, breasts
Males XY and females XX
Determined by sperm
All have the same underdeveloped sex organs at 6 weeks - no difference
Müllerian ducts potential to develop into female sex organs
Wolffian ducts potential to develop into male sex organs
Presence of SRY gene in the Y = SRY protein (TDF). Stimulates medulla of the gonad to develop into testes = testosterone (androgen) which develops penis and scrotum
Also produce AMH which prevents female development
Other genes are thought to be involved Soxa and NRSAI (Nikoliva 2006)
Without Y not protein so no testosterone = mullarian ducts
External reproductive systems develop from one bipotential perecuror
Differences occur in 2nd month - glands, uethral fold, lateral body and labioscrotal swelling
Puberty
Hypothalamus produces gonadotropin releasing hormones to the pituitary which cause gonadotropic hormones (LH and FSH) to be released
Act on either structure
Males - cause tested to produce T and sperm. T to dihydrotestosteroe which. Triggers growth and development of penis
Females - estrogen and progesterone coordinate the first menstrual cycle
secondary sexual characteristics occur due to adrenocorticotropic hormones …
Levels of androgen change fatty acid composition of perspiration resulting in an adult odour and secrete oil increasing risk of acne
Reproductive behaviours require remodelling and activation of neural circuits involved in salience of sexual stimuli, sensory associations, sexual motivation and performance
Hormonal peaks mark chsnges in behaviour
T - sex Drive, mood swings, reduced attention span and agg
Sexual differentiation - organisation effects
Hard to study in humans - animals and disorders of sexual development
Organisational effects prenatally lead to typical behaviours
Males - MPA key in stimulation of sexual behaviour - destruction = no sexual behaviour and stimulation = sex Drive. Contains a larger nucleus, the sexually dimorphic nucleus (3-7x) than women size is influenced by androgens
Human equivalent - INAH (2-3x larger)
Females - VMH stimulates sexual behaviour and destroying it abolished behaviour
Injection into VHM stimulates sexual behaviour even when ovaries are not there - doesn’t need hormones to develop
Androgens stimulate development of brain areas that respond to T in adulthood - behavioural maculation
Castration prevents male behaviour because the MPA isn’t developed
Also lead to behavioural defeminisation by interfering with areas that respond to oestrogen - VHM does not need hormones to develop so it has to be stopped (ovari-ectomy followed by T = no female sexual behaviour
Activational effects
Females rats - ovarian hormones control willingness to mate so animals only mate when the female is fertile
Humans - ability to mate not controlled by hormones but may influence sexual interest
Males - no different from rats
Depends on T normal levels = fertile / sex Drive
Low levels = sperm production ceases
Environment can change T levels - anticipation of sex
Sex hormones effect development of sex organs and influence behaviour by interaction with the nervous system
Prenatal androgen effects nervous system (organisational) and adult androgens activate structures that drive behaviour
Sexual development disorders
“Woman who wasn’t”
Anne chromosome XY
Has internalised tested and no ovaries, hormones matched a mans
Had androgentic insensitivity- doesn’t respond to androgen so VMH leads to the development of female secondary characteristics as it’s doesn’t need hormones to develop
“Little girl who grew into a boy”
Born with ambiguous genitals but raised as a girl - developed male secondary characteristics at puberty
Low cortisol lead to overproduction of androgens
Adrenogenital syndrome
“Twin who lost his penis”
Born male but due to accident in circumcision penis was rendered useless
Less psychological damaging to be raised as a girl - artificial vagina
Never happy and acted like a lad - toilet standing up
Became a man later on when told
Ideal case as twin had same genetic make up
Biology is the key to gender
Prenatal process of sexual differentiation has a powerful effect on life behaviour despite castration - partly determined by biology
Barista boys
Born and raised as girls a XY gene mutation meant male sex organs developed at puberty and developed a penis - once biology changed so did the ‘girls’ gender
Hormonal effects
Vandenburg 2003
Female foetuses who are next to males so are exposed to more T show more masculine behaviour
Money and Ehrhart
Human mothers who took hormones to cease bleeding in pregnancy gave birth to more Tomboyish girls
Yalom
Human mothers who took female hormones during pregnancy gave birth to more feminine boys
Hormones have an impact during prenatal development which effect future behaviour
Differences in the brain
Testosterone impacts how the brain develops it can slow and speed up growth
Maculation of foetal brain results in male sexual behaviour
Geshwind
During pregnancy of boys the left hemisphere growth is slowed (language) and the right (spatial awareness) is fast
Men have a thicker right hem - superior spatial awareness (driving, logical)
Women then have a thicker left side in comparison - better at verbal reasoning
Driesen and raz
The corpus callosum (fibres between sides) are bigger in women and explains superior emotional intelligence
Paternal investment
Females invest more as they have less eggs which are more costly to produce than sperm
Can have a limited number of offspring
So they are more careful with choosing a partner
Females give greater prenatal and postnatal care
Males invest less because they can’t be sure the child is theirs - protect them selfs from the possibility of cuckoldry
Therefore are concerned with fidelity of mates - Buss suggests men are more jealous of the sexual act and women of the emotional betrayal and shift of resources - males were more aroused at sexual betrayal- Harris stars they will aroused at any sexual content
Male competition
Intrasexual selection
Males compete with one another for members of the opposite sex, victors are able to mate and pass on their genes and the trait which leads them to success is passed on to the next generation
Fighting off competition to deter other males from approaching a female maximised opportunity to mate and pass of genes.
Competition benefited women as it ensure the best genes for her offspring and ensures resources - could be why sex hormones are linked to aggression
Mating strategies
Sexual selection and investment effect mating preferences
The more females a man impregnates the higher his reproductive fitness and the little investment means that men tend to adopt short term mating whereas for women this has higher consequences
Clarke and Hatfield- will you sleep with me? 75% of makes said yes
Monogamy
In humans this appears to be the norm across cultures
Promiscuity is frowned upon
Monogamy is needed due to care of human infants
However doesn’t alway work out
UK divorce rate is over 40%
And if those not divorced - infidelity rates are very high 25-80%
Biologically due to one person doesn’t possess all commonly desires characteristics and ensures wider spread of genes
Mate selection
Buss
Mate preferences in 10,000 pps in 37 countries
Males preferred younger females with an hourglass figure - signs of fertility
Females wanted strong men with access to resources
Penton-voak
Female choice varies across the menstrual cycle - feminised face when not at high risk of conception and masculine face at high risk - ensures good genes
Miller
Males preferences also depend on fertility
Naturally menstruating lap dancers warmer more when in fertile period than those on the pill
Roberts
Men also judge faces and scent as more attractive when a women is fertile
Sexual orientation
Social
Suggest parents have an influence
Bell and Hammersmith 1981
Large study of male and female homosexuals - no evidence that being raised by a dominant mother and submissive farther lead to homosexuality - reported feelings were the best predictor
Sexual orientation
Biological
Sex hormones
Meyer 1984
Levels of sex steroids similar in homosexuals and heterosexuals but 30% lesbians had high testosterone - cause of and effect of life style?
Money
Studies 30 women with CAH ( excessive androgens, show maculation of genitals) 48% were homo or bi sexual - exposure to androgens effects it
Birth order - higher chance as a function of older brother
Alexander - mother may become tolerant to testosterone and so might deactivate the mmascuilising Hormones
Stress of mothers can interfere with androgen production so organisational effects don’t occur - typical male behaviour is avoided as the SDN in the MPA is surpressed (Kinsey and svare)
The INAH is larger in heterosexual than homo - not a consistent finding
Bailey and pillard
Would see concordance in twins- male MZ twins show 52% Dz 22
Female twins show 48% Dz 16
Although more MZ twins than DZ should concordance the majority don’t do the environment is just as important
