Chapter 6: Inheritance and Evolution

1. Chapter 6: Inheritance and Evolution Theories of Personality February 14, 2003 Class #4

2. Somatotypes • Can you tell someone’s personality by their body type?

3. William Sheldon(1898-1977) • Was an American psychologist who devoted his professional life to observing the range of human body types and he associatedthese tohuman personality traits or temperament types • Born in Pawtuxet, Rhode Island his family was poor, but not poverty stricken • His father farmed and hunted for a living

4. Sheldon’s Biography • Sheldon graduated from Warwick High School in 1915 and entered Brown University • With the American entrance into World War I he was commissioned as a 2nd lieutenant in a machine gun company • In 1919 he received a degree from Brown in absentia, and afterwards not really settled on a career he wandered westward • He entered the University of Colorado where he earned an M.A. in English in 1923

5. Sheldon’s Biography • Around this time he had meetings with Freud and later with Jung concerning psychological concerns that had interested him and he also meet with German psychiatrist Ernst Kretschmer who had started the scientific study of the relationship between physique and personality • He finally decides to pursue psychology at the University Chicago where he received his Ph.D. in 1925 • He taught psychology at the Univ. of Chicago and then at the University of Wisconsin

6. Sheldon’s Biography • He became very interested in Freudian ideas and also in how physical characteristics might influence personality • He read how William James (one of psychology’s founding fathers) had gone through medical school not to practice medicine but to become a better psychologist and religious philosopher…so he does the same • He enters the University of Chicago Medical School and received an M.D. in 1933

7. Sheldon’s Biography • During the late 30’s and early 40’s he dedicated himself to researching the thesis linking one’s physical features and psychological tendencies • Eventually, he was invited to work at Harvard where he conducted his most famous study • In 1942, World War II broke out and he enlisted – eventually earning the rank of major in the army • Stationed in Texas he was permitted to continue his research on somatotypes

8. Sheldon’s Biography • Unfortunately in 1945, he was struck down by a severe lymphatic cancer and given a medical discharge with 100% disability • He was not expected to live more than a year… • Interestingly, he made a remarkable recovery and became busier than ever before • He was instrumental in the opening of somatotype clinics on both the east and west coasts • His health probably began to fail again in the late 60’s and he basically retired at that point but he did live until 1977 (over 30 years longer than the doctors had predicted)

9. Sheldon (1942) • In original study at Harvard, he and his colleagues examined thousands of photographs of almost completely nude male bodies and concluded we have three components to our physiques…

10. Somatotypes • Endomorphs • Mesomorphs • Ectomorphs

11. Endomorphic Body Type • Physique • Tendency towards plumpness • Soft body • Underdeveloped muscles • Round shaped • Over-developed digestive system

12. Can’t help but think of John Candy in “Planes, Trains, and Automobiles”… • Personality • Sociable • Amiable • Needy for affection and approval • Love of food • Tolerant • Evenness of emotions • Love of comfort • Good humored • Relaxed

13. Mesomorphic Body Type • Physical • Tendency towards muscularity • Hard, muscular body • Overly mature appearance • Rectangular shaped • Thick skin • Upright posture

14. Bruce Willis comes to mind… • Personality • Adventurous • Desire for power and dominance • Courageous • Indifference to what others think or want • Assertive, bold • Zest for physical activity • Competitive • Love of risk and chance • Dominating

15. Ectomorphic Body Type • Physical • Thin • Flat chest • Delicate build • Young appearance • Tall • Lightly muscled • Stoop-shouldered • Large brain

16. Manute Bol??? • Personality • Self-conscious • Preference for privacy • Introverted • Inhibited • Socially anxious • Artistic • Mentally intense • Emotionally restrained

17. Somatotypes • A person’s somatotype was defined by placing the individual at some point along each dimension • Your somatotype is designated by three numbers each ranging from 1-7 indicating the degree of each body type • Receiving a 1 would mean a person had none of the usual characteristics of that body type • Receiving a 7 would mean they would have all of the characteristics of that body type

18. Sheldon’s Temperaments • He also gave the subjects personality tests and categorized them into the following: • Viscerotonia – • Easygoing, relaxed, sociability • Somatotonia – • Courage, assertiveness, physical activity • Cerebrotonia • Tendency towards privacy, avoidance

19. High correlations between physique and temperament • Endomorphs and Viscerotonia • Mesomorphs and Somatotonia • Ectomorphs and Cerebrotonia

20. Criticisms of Sheldon’s research… • Experimenter bias • Self-Fulfilling Prophecies

21. Experimenter bias??? • Sheldon found exactly what he had hoped to find… • But other researchers have failed to find the strong relationship between somatotype and personality reported by Sheldon • One of the main problems with Sheldon’s research was that he rated both the somatotypes and the temperaments of his subjects • This provided room for experimenter bias, perhaps making his ratings support his theory more than they should have

22. Self-Fulfilling Prophecies??? • This one’s not really a flaw in Sheldon’s research but expectations of others can somehow produce behaviors • So, maybe its not really the body type but how others are reacting to that body type that’s influencing personality?

23. What type was Sheldon himself? • His somatotype? • He was around a 3.5 - 3.5 - 5, and thus he falls sort of in the middle which more ectomorphic tendencies than the others • His psychological type? • From reading his biography he probably was an introverted thinking type

24. Heredity and Personality • A century ago Francis Galton insisted that nature prevails enormously over nurture • Today those, like Galton, who believe that heredity molds personality assume that evolution has provided us with inborn behavioral tendencies that differ from person to person

25. Behavioral Genetics • This field studies the relationship between heredity and behavior… • Research in behavioral genetics has shown that even newborn infants exhibit differences in temperament • Some are emotionally placid, others are emotionally reactive

26. How it applies to the development of personality… • Initial differences in temperament might contribute to the development of differences in personality… • They might affect how infants respond to other people and, in turn, how other people respond to them • For example, a placid infant would be less responsive to other people • As a consequence, others would be less responsive to the infant • This might predispose the infant to become less sociable later in childhood, laying the groundwork for an introverted adult personality

27. Buss and Plomin (1984) • They felt that the following personality dispositions were our temperaments and that these were inherited personality traits present almost immediately in early childhood… • Activity level • Overall energy level (vigor and speed) • Sociability • Interaction vs. isolation • Emotionality • Physical arousal levels

28. Buss and Plomin (1984) • Temperaments are different from other traits because they are genetically based • They are more influential on personality and ultimately behaviors • They affect personality throughout life span • Although, they may be modified by experiences

29. Methods used in determining the role of inheritance in personality • Twin Study Method • Adoption Research

30. Twin Studies • Monozygotic • Identical twins (one-egg) • Dizygotic • Not identical • Resemble one another as much as any brother or sister would

31. Twin Studies • Do identical twins who are adopted by separate families act like one another more than say two adopted children into the same family who have no genetic influences?

32. Bouchard’s Twin Studies • Thomas Bouchard’s University of Minnesota twin studies (1970-1984) • Research done in Twin Cities of Minneapolis/St. Paul, MN • Oskar and Jack • The Jim Twins • Uncanny coincidences???

33. Adoption Studies • Surprising finding from hundred’s of studies: • People who grow up together, whether biologically related or not – DO NOT much resemble one another in personality • Developmental Psych’s big puzzle: • Why are children in the same family so different??? • But adoptees are more similar to biological parents than adoptive parents

34. Inheritance and Sexual Orientation • Random Telephone Surveys in North America: • About 3-5% of the adult population acknowledges that they are homosexual or bisexual • Many feel that this is an underestimate

35. Lippa (2001) • Survey of 721 students in four large human sexuality classes at California State University, Fullerton • Subjects:287 men and 434 women • Average age = 22 years • 42% White • 22% Hispanic • 21% Asian • 15% "Others“

36. Lippa (2001) • Males: • 2% self-labeled as "gay“ • 3% as "bisexual" • Women: • 1% self-labeled as "lesbian" • 3% as bisexual

37. Why is someone gay or straight? • Psychologists really don’t fully understand the causes of sexual orientation • Lets look at some biological explanations… • Concordance rates: MZ > DZ • A homosexual gene? • LeVay (1991): INAH3

38. Concordance rates • Eysenck (1964) • Reported a higher incidence of homosexuality among men whose MZ twin was gay than among men whose DZ twin was gay • Bailey and Pallard (1991) • Twin study • Homosexual men • Co-twin was more than twice as likely to be homosexual if the twins were MZ • Bailey, Pallard, Neale, & Agyei (1993) • Replicated earlier study using homosexual women • Same results

39. A homosexual gene? • Hamer et al. (1993) • Examined families of homosexual men • Found significantly more gay relatives on mother’s side of family • Maternal uncles and sons of maternal aunts (male cousins) • Might their be a homosexual gene on the X chromosome?

40. Hamer et al. (1993) • They continued the investigation and found that most of the homosexual men had a region in the X chromosome that was similar suggesting a genetic basis… • But not for all suggesting another reason • Important implication to all this: • It may be possible for non-homosexual women to pass on this gene

41. CONTROVERSIAL RESEARCH • Dean Hamer, left, and J. Michael Bailey converse at a conference last May

42. The biological basis of sexual orientation is a research area that is coming out of the closet • Much of the field's current visibility is due to the wide publicity surrounding neuroanatomist Simon LeVay's 1991 study of INAH3-the third interstitial nucleus of the anterior hypothalamus-which is three times larger in men than in women

43. LeVay (1991) • Examined hypothalamic tissue from: • 19 gay men, all of whom died of AIDS • 16 heterosexual men, six of whom had died of AIDS • 6 women of unknown sexual orientation

44. LeVay (1991) • Found neuroanatomic differences between homosexual and heterosexual men… • INAH3 was two to three times larger in heterosexual men than in gay men

45. LeVay (1991) • As the first suggestion that there was a neuroanatomic difference between gay and heterosexual men, LeVay's finding garnered a great deal of public attention, and a great deal of controversy about both its scientific and its social implications

46. Is there a genetic risk for divorce? • McGue and Lykken (1992) • Study suggests that divorce is genetically based rather than environmentally based as it is commonly viewed • 1516 pairs of same-sex twins • 722 MZ and 794 DZ • Results: MZ > DZ • If co-twin is divorced, risk for MZ twin is 45% and risk for DZ twin is 30% • Implies genetic influence while casting some doubt on environmental influences

47. McGue and Lykken (1992) • The researchers suggest that this genetic influence is mediated largely by inherited personality characteristics, such as impulsivity and moral conviction • Further they suggested that while cultural factors may influence the threshold for divorce within a given culture, variations in underlying aggregate risk are strongly influenced by genetic factors