Biological Psych 23 Personal Identity Gender Sex differences = biological Gender differences = thinking Sexual differentiation How identify sexually What call self (male-female) Sexual differentiation begins with chromosomes Female = XX chromosome Males = XY Prenatal Start with same anatomy Müllerian ducts Lead to female internals Wolffian ducts Lead to male internals Male (XY) Y Chromosome SRY (sex-determining region) Causing primitive gonads to become testes Testes Sperm-producing organs Produce androgens (male hormone) Wolffian ducts develop into: seminal vesicles: store semen vas deferens: duct from testes into penis Müllerian inhibiting hormone Peptide hormone Müllerian ducts degenerate Testosterone Development of penis & scrotum Females (XX) More estrogen than androgens Primitive gonads become ovaries (egg-producing organs) Wolffian ducts degenerate Müllerian ducts develop Estrogen
Steroid Hormones four carbon rings derived from cholesterol 3 effects: 1. bind to chromosomes activate or inactivate genes 2. bind to membrane receptors like protein or peptide hormones 3. enter cells activate proteins in cytoplasm Androgens and Estrogens Not a specific chemical itself Androgens promote masculine features (hair) Estrogens promote female features (breasts) Testosterone most widely known androgen Estradiol most prominent type of estrogen higher levels in women Progesterone Predominantly female Prepares uterus implantation Maintains pregnancy Organizing effects mostly during critical stage determine develop as male or female Activating effects Temporary Only when hormone present Can occur at any time in life Sensitive period When event has long-lasting effect Testosterone impacts external genitalia in 3 rd - 4 th month of pregnancy In Hypothalamus Sexually dimorphic nucleus
Part of medial preoptic hypothalamus Larger in male than female Linked to male sexual behavior Females can generate cyclic pattern of hormone release Males can t Alpha-fetoprotein Protein that binds with estrogen Present in early sensitive period Prevents females being masculinized by their own estrogen Childhood Behavior 3-8 months old Show preference for toys Girls look at dolls more Boys look at dolls & trucks equally Male monkeys lay with trucks and balls more Female monkeys play with dolls Prenatal injections of testosterone After born, play more like boys Activating Effects of Hormones Change behav. by enhancing $ Testosterone need for male sexual arousal Estrogens increase sensitivity of pudendal nerve Brain (rat studies) Low concentrations of dopamine facilitate penile erection sexually receptive postures in female High concentrations of dopamine orgasm Males prefer cage where previously had sex Female rats find sex reinforcing only if they get to decide when it occurs -- how know? Humans High Testosterone seek more sexual partners even after marry or have long-term relationship Low Testosterone decrease sexual activity
Testosterone levels don t change after marriage Low T more likely to marry Single women high T Long-term partner have low T either homosexual or heterosexual Impotence Men Inability to have erection not usually caused by low T Treated by increasing blood circulation in penis & hypothalamus Gender Identity Intersexes Male & female characteristics Hermaphrodites Genitals-genetic sex mismatch Some normal testicular tissue plus ovarian tissue Congenital adrenal hyperplasia Overdeveloped adrenals Excess release of testosterone In genetic males extra testosterone little effect In genetic females Masculine physical char. clitoris may resemble penis Treated different by teachers Differ in childhood interests More interested in rough sports More aggressive as adults Less interested in infants Create or lengthened vagina Significant sexual difficulties No romantic attraction to men Little or no interest in sex Lack of orgasm Testicular Feminization
Androgen insensitivity Not bind to genes in nucleus Genetic male Appearance of female Small penis Considered female until puberty Don t menstruate Gender Assignment In 1950s Most intersexed reared as girls Surgery easier to look like girl Most developed male interests Demanded reassignment as males Now Recommend honesty No bias toward female Use predominant external appearance as gender No surgery now Change sexual orientation later? Sexual Appearance Genetic males Enzyme (5 -reductase 2) converts testosterone to dihydrotestosterone Inbreeding genetic disorder blocks enzyme penis not develop until puberty identified as female as birth Boys usually want to switch to male gender identity Reassignment when teen common if: born without penis lost penis through accident Gender roles 3-8 months old Girls look at dolls more often Boys dolls & trucks equally Monkeys Girl play more w/ dolls Boys play with trucks & balls Testosterone injected prenatal Girl monkey more masculine-type play after born
Single women Have higher testosterone levels than have long-term partner (homosexual or heterosexual) Multiple Mates Men more interested in short-term sexual relationships with many partners Evolutionarily, both work for men: One-mate strategies Multiple-mate strategy Women have less to gain Limited number of pregnancies But can upgrade to better mate Mate Seeking Both men & women prefer Healthy Intelligent Honest Attractive Women prefer: Good providers strongest when no $ of own Strong commitment Body odor Women prefer differ from hers immune genes dissimilar Men strongly prefer younger Differences in Jealousy Men upset by sex infidelity Women upset by emotional infidelity Evolved or Learned Anatomical Differences Longer arms, legs & hands In heterosexual men In homosexual women Brain Differences Larger in gay men anterior commissure Pain bilateral connections
suprachiasmatic nucleus (SCN) Circadian rhythms Processing Differences Landmarks for giving directions Gay men Heterosexual women Sexual Orientation Not an arbitrary decision Integral part of person Homosexuality is a shift toward In some aspects, not others Genetics Homosexuality Highest in monozygotic twins Lower in dizygotic twins Still lower in siblings Higher incidence among maternal relatives Prenatal Influences Lowest in oldest sons Mother s immune system can react against a protein in 1st son Attacks subsequent sons more Attraction Women Periovulatory period Mid-point of menstrual cycle Sexual interest increases High estrogen levels Prefer en who look and act more masculine Oxytocin stimulates contractions of uterus during delivery Stimulates mammary gland to release milk Also releases at orgasm relaxation & less anxiety Bonding of couples Mother-child? Facilitates social behaviors Recognizing familiar faces Recognizing blurry words (like love or kissing) Hormones increase activity in medial preoptic area
anterior hypothalamus Men Vasopressin Important for parental behavior Male prairie voles high levels of vasopressin long-term pair bonds help rear their young Interest in Multiple Mates Men interested in short-term sexual relationships many partners Pheromones Chemicals Released by an animal Impact members of same species Affect behavior (ie., sexually) Vomeronasal organ (VNO) Located near smell receptors Separate system Respond only to pheromones Each VNO receptor responds to just one pheromone No adaptation from continued exposure VNO is very small in humans No receptors have been found Have one type pheromone receptor located in olfactory mucosa Synchronize menstrual cycles Spend a lot of time together Enhance regularity of menstrual cycle For long-term relationships Body Image Facial symmetry Very difficult to find Takes billons of cells In same places on each side Men should have: broad forehead relatively longer lower face prominent chin and brow
defined cheekbones chiseled jaw Women should have: Baby face Large eyes Small nose Narrow jaw High cheekbones Fatter than they think should be Ratios Between eyes 46% of total width Between eyes & mouth 36% of total height Jessica Alba Overestimation Men value of muscles Women value of thinness Eating Disorders Obesity in rats Buffet of high-calorie foods Can t pass up options Become obese Lose interest in other rewards Fat is not happy Small correlation between obesity and mood Obesity not caused by depression Prenatal high-fat diet before increase appetite & body weight Genetics and Body Weight Danish study weights of adopted children correlate with biological parents Genetic or prenatal Specific genes Mutated gene for melanocortin can cause obesity
Syndromal obesity From medical condition Prader-Willi syndrome Genetic disorder leads to obesity high levels of ghrelin (peptide) Weight Loss Dieting rarely effective alone Maintaining diet Implement small changes 20-40% success (2 years) Increasing exercise Decreasing eating Fructose doesn t $ satiety path Non-diet drinks high in fructose Artificial sugars cause body to unlearn association between sweet and calories? Sibutramine (Meridia) Appetite suppressants Orlistat (Xenical) Block fat absorption Gastric bypass surgery Removes part of stomach Smaller meals produce satiety Bulimia Nervosa Alternate dieting & overeating Some vomit after meals. Most suffer from depression Results in: Lower levels of CCK (hormone) Increased ghrelin (hormone) Altered NT transmitters regulate eating Similar to drug addiction Food activates nucleus accumbens