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Evol-Sex

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Gender-Role Standards and

Stereotypes

Sex stereotypes that men are more

aggressive than women and women more

interpersonally sensitive than men are

very robust, even among more educated

people, both sexes, all social classes.



– Probably because they have some

truth in them!

– Keep in mind that male/female

distributions overlap.

Gender differences



 NOTE: There are overlaps in all of these areas so that, for example, some

girls are more physically aggressive than some boys. Physical Sex

Differences:



 Girls more advanced physically throughout childhood; they mature earlier

and their development stops sooner.

 Boys have larger lungs and heart, and they are superior at activities

involving gross motor activities and strength; males more likely to suffer a

wide range of developmental disorders (speech defects, ADHD, mental

retardation), genetic defects (because of x-linkage; WHY?), and are more

susceptible to malnutrition and disease.

 Boys are more physically active; in preschool they are more likely than

girls to play in a physically active style in larger groups away from the

teacher.

 Girls tend to have a few intimate friends

 Boys have a larger number of "pals"—guys they hang out with but don't

have close, intimate, confiding relationships.

Gender differences



 Cognitive Sex Differences:

– Girls superior at verbal abilities (vocabulary, reading comprehension, verbal

creativity) during early to middle childhood. These differences become

attenuated as children get older, and disappear by adolescence.

– Boys have greater visual-spatial ability beginning around age 10. (Visual-

spatial ability is involved in manipulating objects in two- or three-dimensional

space, reading maps, aiming at a target.)

– Boys also excel at mathematics beginning around age 12.



 Some studies indicate that boys have a higher IQ on average than girls by

late adolescence (~4 IQ points).

– Theory: Girls' development ends sooner than boys, and boys continue to

develop. This is controversial.



 Girls superior in Conscientiousness: Focused attention, responsibility,

dependability, delay of gratification.

– Conscientiousness is strongly correlated with school success.

Gender differences



 Social Sex Differences:

– Boys more aggressive, especially physical aggression and direct

verbal assault. (Girls use indirect forms of aggression such as

exclusion, negative gossip.)

– Boys more into risk-taking and sensation seeking as well as

curiosity and exploratory behavior; boys attracted to physically

dangerous occupations

– Girls more compliant with demands of parents and teachers.

(Conscientiousness)

– No sex differences in attachment classification. However, Girls

more nurturant and dependent. (Affectional System) Infant girls

more attracted to faces and may recognize mother's face earlier.

– Girls more fearful of possible personal threats and dangers. No

sex differences for social phobias, or possibly more common

among boys.

Gender differences



 Sex Differences in Atypical Development:

– Boys more likely to have genetic defects, physical disabilities, mental

retardation, reading disabilities, speech defects, and school and emotional

problems.

– Boys are more likely to have genetic defects because of x-linkage: Boys only

have one X-chromosome and therefore any recessive gene on the X-

chromosome is expressed. Girls are likely to get a dominant normal gene from

their father's X-chromosome.

– Boys are "the less canalized sex"—they are more open to environmental

influences, including negative environmental influences. This may be seen as a

high risk strategy. Boys are more vulnerable to stress such as family

disharmony.

 The evolutionary theory of sex (see below) implies that boys are expected

to be the high risk sex in general; this is related to the finding that boys are

more aggressive and more attracted to sensation seeking. Both aggression

and sensation seeking are high risk/high reward undertakings.

Developmental Patterns of Gender Typing



 15- to 36-month-old toddlers have clear preferences for toys that are

"gender appropriate"; but girls are more likely than boys to choose "gender

inappropriate" toys.

 In general, the male role is more clearly defined: there is a narrower range

of activities considered appropriate for males.

– Boys who play with "girl" toys or retreat in the face of aggression "fear

derision" (p. 558). "Although we tolerate tomboys, we reject sissies" (pp. 558).

– The condemnation comes from both parents (especially fathers) and peers.

 Based on survey data, boys in the US like guns, boxing, wrestling and

karate, team sports, and fixing and making things more than girls.

Girls prefer dolls, sewing, cooking, dancing, and looking after younger

children more than boys.

 Parents encourage these patterns by, for example, assigning household

tasks.

– "Even in the 21st century, girls are more likely to make beds, clean, prepare

meals, wash dishes, and do laundry. Boys are more likely to fix things, take out

the garbage, and mow lawns" (p. 559).

Stability of Gender Typing



 Masculinity and femininity develop early and are

stable personality characteristics.

– This is not surprising, since many of the traits that

show sex differences are linked to personality

systems.

– There is some change in later adulthood as men

become more nurturant and expressive, especially in

old age.

 Probably due to less testosterone.



Biological Factors in Gender Differences:

HORMONES AND SOCIAL BEHAVIOR

 Women have small amounts of the male hormone testosterone

and men have small amounts of female hormones like

progesterone and estrogen. In childhood, the differences are

quite small, but they increase markedly in adolescents and

adults.



 There are two surges of hormones, prenatally and during

adolescence.

– The surge of hormones prenatally affects behavior in childhood, and

the surge during adolescence activates and enhances the early

predispositions created by the prenatal surge.

– These are critical periods for the effects of hormones on later behavior.

Biological Factors in Gender Differences:

HORMONES AND SOCIAL BEHAVIOR

 Animal studies: Young, Goy, and Phoenix (1967)

injected female monkeys with testosterone prenatally

or around the time of birth.

– Genetic female offspring were

pseudohermaphrodites. Their genitalia were more

masculine (large clitoris), and their behavior was

also masculine (more aggressive, more mounting

behavior [a male mating behavior], more rough

and tumble play, more socially dominant).

– Similar behaviors are elicited in genetically female

rodents injected with testosterone.

Biological Factors in Gender Differences:

HORMONES AND SOCIAL BEHAVIOR



 NOTE: Levels of testosterone are also

influenced by the animal's experience.

Animals that have been repeatedly defeated in

fighting have lowered testosterone, and

winners have elevated testosterone as a result

of their experience.

– This also occurs with humans: Winning an athletic

event results in a surge in testosterone.

Biological Factors in Gender Differences:

HORMONES AND SOCIAL BEHAVIOR

 Human Studies: Girls who have received testosterone or

testosterone-like hormones prenatally have masculinized

behavior.

– These girls are genetic females but their genetalia are typically

masculinized at birth (enlarged clitoris, fused labia that resemble a

scrotum).

– They often receive an operation to make her appear more feminine.

– These girls have masculinized behavior: Tomboyish, liked vigorous

athletic activities, simply utilitarian clothing; little interest in dolls,

babysitting, or caring for younger children, jewelry, cosmetics, or hair

styles.

– They also had a more male-type achievement pattern and male-type

attitudes toward sexuality. They preferred boys as playmates and boys'

toys.

Biological Factors in Gender Differences:

HORMONES AND SOCIAL BEHAVIOR



 HORMONES AND COGNITIVE SKILLS

– There is evidence for a critical period for brain

organization and hemisphere lateralization (males

more lateralized).

– Testosterone surge prenatally is responsible. This

surge makes females process verbal information

better and males process spatial information better.

– Female fetuses exposed to abnormally high levels of

androgens are better at spatial abilities.

Sex differences in Spatial

Reasoning

 Water task; Light bulb in a car going uphill:

 Male advantage is only found for spatial (geometric)

ability, not for computational ability, basic math skills or

algebra.

– Biological influences do not rule out environmental influences.

– Text notes that the differences are relatively small (but small

differences lead to large differences in proportions at the high

end of the distribution).

– Girls enroll in progressively fewer math courses over the high

school and college years. Even girls with superior math ability

seem less interested in math as they get older (e.g., 34% of

advanced physics classes). But the gender gap is narrowing.

BRAIN LATERALIZATION:



 Brain becomes increasingly specialized with age, with right

hemisphere more specialized for spatial tasks and left hemisphere

more specialized for verbal tasks. Women who suffer left

hemisphere damage are less likely to have damage to verbal

abilities.



 In a task where children had to identify objects inside a bag, sight

unseen, boys were better when feeling with their left hand

(controlled by the spatial centers in the right hemisphere). For girls

there was no difference between hands in their ability to identify

objects.



 In a rhyming task where subjects were asked if nonsense words

rhymed, both sides of women's brains were activated. For men, only

the left hemisphere (underlying verbal abilities) was activated.

Evolutionary Psychology: Theory of

Sex: Robert Trivers (1972)

 1.) MALES DEFINED AS SEX WITH SMALL GAMETES,

FEMALES ARE SEX WITH LARGE GAMETES





 2.) FEMALES TEND TO INVEST MORE IN

REPRODUCTION THAN MALES.

– TYPICAL MAMMALIAN FEMALE: PREGNANCY, LACTATION,

CAREGIVING'VERY HIGH COST IN TIME AND ENERGY

TYPICAL MAMMALIAN MALE: SPERM'VERY LOW COST

.

Evolutionary Psychology: Theory of

Sex: Robert Trivers (1972)

 3.) ECONOMICS 101: WHEN YOU HOLD

VALUABLE RESOURCES, YOU DON'T GIVE THEM

AWAY.

– FEMALES EXPECTED TO BE SELECTIVE,

DISCRIMINATING MATERS

– FEMALES WANT:

MALES WHO WILL INVEST IN OFFSPRING,

MALES WITH GOOD GENES, HIGH SOCIAL STATUS,

ETC.

Evolutionary Psychology: Theory of

Sex: Robert Trivers (1972)

 4.) ECONOMICS 101: MALES DO NOT HOLD RESOURCES. THEREFORE THEY MUST

COMPETE IN ORDER TO GET THEM. THIS RESULTS IN THE PREDICTION THAT

MALES WILL BE MORE AGGRESSIVE.

 IN GENERAL, MALES MUST COMPETE FOR FEMALES, AND THE MAIN OBSTACLE IS

OTHER MALES:

– ELEPHANT SEALS: DEFEATING MALES IN COMBAT

– CHINESE EMPERORS: CONTROLLING MALES AND FEMALES

– MOVIE STARS

– SUCCESFUL HUNTERS in hunter-gatherer societies;

– RICH MEN IN ALL SOCIETIES ARE ATTRACTIVE TO FEMALES (The Anna Nicole

Smith

phenomenon)

Evolutionary Psychology: Theory of

Sex: Robert Trivers (1972)

 4. (Cont.) MALES HAVE MORE TO GAIN BY BEING HIGH ON AGGRESSION,

RISK-TAKING, SENSATION-SEEKING, SOCIAL DOMINANCE: SUCCESSFUL

MALE CAN MATE POLYGYNOUSLY,



 SUCCESSFUL FEMALE CAN MATE ONLY ONCE.



 EVEN IN A MONOGAMOUS SYSTEM, SUCCESSFUL MALES WILL HAVE

ACCESS TO HIGHER QUALITY FEMALES (MORE NURTURANT, MORE PRONE

TO FIDELITY, HIGHER INTELLIGENCE, ETC.) RISK-TAKING AND SOCIAL

DOMINANCE PAY OFF MORE FOR MEN.



 THEREFORE MEN GAIN MORE BY CONTROLLING SOCIETY (PATRIARCHY),

AND THEY GAIN MORE BY GOING TO WAR.

Evolutionary Psychology: Theory of

Sex: Predictions

 WHEN GENGHIS KHAN AND THE MONGOLS

CONQUERED MOST OF ASIA, THEY REALIZED

AN ENORMOUS GENETIC PAYOFF BECAUSE

THEY ESTABLISHED HAREMS WHEREVER

THEY WENT.

– THE MONGOL Y-CHROMOSOME IS STILL FOUND

AT HIGH FREQUENCIES IN ALL THE AREAS THEY

CONQUERED. ~32 million direct descendants

– A MONGOL FEMALE WOULD NOT HAVE

SIMILARLY BENEFITED BY THIS SORT OF

CONQUEST.

Evolutionary Psychology: Theory of

Sex: Predictions



 FEMALES ADOPT A MORE CONSERVATIVE

STRATEGY: HIGHER ON FEAR, BEHAVIORAL

INHIBITION.

 FEMALES ALSO EXPECTED TO BE MORE

NURTURANT AND LOVING AS MATE

DISCRIMINATION SYSTEM (females benefit by

choosing males who love them and are willing to

invest in their children) AND BECAUSE OF ITS

ROLE IN NURTURANCE (females who are high on

affectional system are prone to nurturance).

Evolutionary Psychology: Theory of

Sex: Predictions



 Male sexual jealousy more directed at

ensuring paternity confidence.

 Female sexual jealousy more directed at

ensuring continued affection as a sign of

continued support.

The End



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