Nature, Nurture & Human Diversity

1. Nature, Nurture & Human Diversity

2. Nature vs. Nurture • If Jaden Agassi, son of tennis stars Andre Agassi and Stephanie Graf, grows up to be a tennis star, should we attribute his superior talent to his Grand Slam genesor to his growing up in a tennis-rich environment? • This issue is of interest to behavior geneticists who study the relative power and limits of genetic and environmental influences on behavior. • Environment: every non-genetic influence, from prenatal to the people and things around us.

3. Heredity • DNA (deoxyribonucleic acid): contain the genetic code in the sequence of its nitrogenous bases for the synthesis of proteins. • Genes: composed of DNA and carry the genetic code for a specific trait or characteristic • Chromosomes: threadlike structures made up of genes and proteins • Genome: the complete genetic instructions of an organism, consists of all the genes and their genetic material found on the organism’s chromosomes.

4. Heredity (cont’d)

5. Heredity (cont’d)

6. Traits • Trait: a genetically determined characteristic; controlled by a pair of genes (one from mom and one from dad) • Gene Complexes: a group of genes that are responsible for the expression of a given trait. • Heritability: theproportion of variation among individuals in a trait that is attributable to genetic factors. • For example, current estimates place the heritability of intelligence at about 50 to 70 percent.

7. Human Genetics • Human Sex Chromosomes: • Male: XY – Female XX • Humans species number of chromosomes in each somatic cell – 46 • Gametes: sperm and egg each contain 23 chromosomes. • Zygote: when a sperm fertilizes and egg, restoring the human chromosome number to 46. • In the mother’s womb, the male fetus is exposed to testosteronewhich leads to the development of male genitalia. • If low levels of testosterone are released in the uterus, the result is a female.

8. Identical vs. Fraternal Twins

9. Twin Studies • MZ twins = monozygotic (identical ) twins • DZ twins = dizygotic (fraternal) twins • By studying MZ twins and DZ twins the relative importance of genetics and environment expression of traits and behavior • Research findings indicate that identical twins are much more similar than fraternal twins in abilities, personality traits, and even interests.

10. Separated Twins Research • Researchers studied twins separated at birth and re-united later in life. • Similarities were found in intellect, personality, attitudes, abilities, interests, fears, brain waves, and heart rate. • Critics point out that any two strangers of the same sex and age would probably have many coincidental things in common if they were to spend hours comparing their behaviors and life histories. • Furthermore, stories by or about individuals do not constitute scientific data, even if there are many of them.

11. Adoption Studies • Adoption enables comparisons with both genetic and environmental relatives.

12. Adoption Studies (cont’d) • Adoptees' traits bear more similarities to their biological parents than to their care-giving adoptive parents. • However, research does indicate that adoptive parents do influence attitudes, values, faith, manners, and politics. • Clearly nature and nurture shape one's developing personality

13. Temperament • Temperament: refers to a person’s stable emotional reactivity and intensity. • The infant's temperament includes inborn emotional excitability. From the first weeks of life, some babies are more relaxed and cheerful, others are more tense and irritable. • These differences in temperament tend to endure. • For example, the most emotionally intense preschoolers tend to be relatively intense as young adults.

14. Group Differences • If genetic influences help explain individual diversity in traits, can the same be said about group differences? • Individual differences in weight and height are heritable and yet nutritional influences have made westerners heavier and taller than their ancestors were a century ago.

15. Gene-Environment Interactions • Genes can influence traits which affect responses and environment can affect gene activity. • A genetic predisposition that makes a child restless and hyperactive evokes an angry response from his parents. • A stressful environment can trigger genes to manufacture neurotransmitters leading to depression.

16. Molecular Genetics • Molecular geneticists attempt to identify the specific genes that influence behavior. • They search for genes that put people at risk for genetically influenced disorders. • Such research may lead to the early termination of embryos identified with genetic disorders. • The bioethics of the use of such molecular genetic research for such identification must be addressed.

17. Psychology & Evolution • Evolutionary Psychologists: study the evolution of traits and behavior using the principles of natural selection/ • Natural Selection (Darwin) • Overpopulation • Competition for limited resources • Survival of the fittest (those best adapted to the environment) • Reproduction (passing of fittest genes to future generations)

18. Psychology & Evolution (cont’d) • In a changing environment, sexual reproduction and mutations are the two sources of variations that can lead to genetic changes and alterations in inherited traits • A number of human traits have been identified as a result of naturalselection. • Why do infants fear strangers when they become mobile? • Why are most parents so passionately devoted to their children? • Why do people fear spiders and snakes and not electricity and guns?

19. Human Sexuality • Males and females, to a large extent, behave and think similarly. • Differences are most evident in respect to reproductive behaviors. Gender Differences in Sexuality Question Male Female Think about sex everyday 60% 25% Sex for affection 25% 48% Casual sex 54% 19%

20. Human Mating Preferences • Males pass their genes to future generations by mating with multiple youthful and fertile appearing females. • Females look for maturity, dominance, affluence, and boldness in male mates. • Females look for one caring male to mate with since there are higher costs involved with pregnancy, nursing, and child rearing.

21. Critique: Evolution Perspective • Evolutionary psychologists explain these differences by noting that compared with eggs, sperm are cheap. • While a woman cares for a single infant, a man can spread his genes by impregnating other females. • Women most often send their genes into the future by pairing wisely, men by pairing widely. • Critics argue that evolutionary psychologists make too many hindsight explanations. • In addition, much of who we are is not hardwired.

22. Prenatal Environment • Identical twins who share the same placenta are more alike than those who do not, suggesting prenatal influences on psychological development. • One placenta may have a more advantageous placement that provides better nourishment and thus a better placental barrier against viruses. • Even when twins share the same placenta, one may get a richer blood supply and weigh more at birth.

24. Environment & Brain Development • Research indicates that young rats living in enriched environments develop a thicker and heavier brain cortexthan those in impoverished environments. • Stimulated infant rats and premature babies gain weight more rapidly and develop faster neurologically. Experience preserves activated neural connections while allowing unused connections to degenerate.

25. Parental Influences • Research indicates that home influences account for less than 10 percent of siblings’ personality differences. • The fact that two children from the same family are as different from one another as pairs of children selected randomly from the population suggests that parents should feel less pride in their children's successes as well as less guilt over their failures.

26. Peer Influences • Experiences with peers powerfully socialize children. • Immigrant children placed in peer groups of non-immigrants quickly lose their parents' culture. • Teens who start smoking typically have friends who model smoking. • Peers are important in learning cooperation, for finding the road to popularity, and for inventing styles of interaction among people of the same age.

27. Influences of Culture • Culture: the enduring behaviors, ideas, attitudes, and traditions shared by a large group of people and transmitted from one generation to the next. • All cultural groups evolve their own norms, rules that govern their members' behaviors. • Cultures vary in their requirements for personal space, their expressiveness, and their pace of life. • Cultural values impact child-rearing practices. • For example, Westernized cultures raise their children to be independent. • Many Asians and Africans who live in communal cultures focus on cultivating emotional closeness.

28. Influences of Culture (cont’d) • Cultures change over time. The rate of this change may be extremely fast. • In many Western countries, culture has rapidly changed over the past 40 years or so. • This change cannot be attributed to changes in the human gene pool because genes evolve very slowly.

29. Culture & the Self • Individualistic Culture: nurtures an individual’s personal identity • Collectivist Culture: the individual identity is the same as the group identity • Individualist cultures (European) raise their children as independent individuals. • Collectivist cultures (Asian) raise their children as interdependent.

31. Cultural Influences Culture & Child Rearing Westernized Cultures Asian‐African Cultures Responsible for self Responsible to group Follow your conscious Priority to obedience Discover your gifts Be true to family-self Be true to yourself Be loyal to the group Be independent Be interdependent • Despite diverse cultural backgrounds, humans are more similar than different in many ways. • We share the same genetic profile, life cycle, capacity for language, and biological needs.

32. Gender Development • Based on genetic makeup, males and females are similar, since the majority of our inherited genes (22 pairs are autosomes – body chromosomes ) are similar. • Males and females differ biologically in body fat, muscle, height, onset of puberty, and life expectancy.

33. Gender Differences Aggression: • Men express themselves and behave in more aggressive ways than do women. • This aggression gender gap appears in many cultures and at various ages. • In males, the nature of this aggression is physical. Social Power: • In most societies, men are socially dominant and are perceived as such. • In 2005, men accounted for 84% of the governing parliaments.

34. Gender & Connectedness • Males and females differ in their feelings of belonging (connectedness), a disparity that is noticeable from a young age and continues as an individual gets older. • When playing, boys tend to engage in competitive group activity without much close, confidential, or affectionate dialogue. • Girls typically are more intimate with each other and play in smaller groups, frequently with one friend. • Girls are also less competitive and more supportive and empathic.

35. Gender Roles • Gender roles: our expectations of the way men and women should behave. • Gender roles vary across cultures and time. For example, in nomadic societies of food-gathering people, there is little division of labor by sex, so boys and girls receive much the same upbringing. • In agricultural societies, women stay close to home while men often roam more freely. Such societies typically socialize children into more distinct gender roles. • Even among industrialized countries, gender roles vary. • In North America, medicine and dentistry are predominantly male occupations • In Russia, most medical doctors are women, as are most dentists in Denmark.

36. Gender Identity Theories • Gender Identity: our sense of being male or female. • To varying degrees, we also become gender-typed, acquiring a traditional male or female role. • Social learning theory assumes that children learn gender-linked behaviors by observing and imitating significant others and by being rewarded and punished. • Gender schema theory assumes that children learn from their cultures a concept of what it means to be male or female and adjust their behavior accordingly.

37. Influencing Personal Development