The Psychology of the Person Chapter 10 Biological Research

The Psychology of the PersonThe Psychology of the PersonChapter 10 Biological ResearchChapter 10 Biological Research

Naomi Wagner, Ph.DNaomi Wagner, Ph.DLecture Outlines Lecture Outlines

Based on Burger, 8Based on Burger, 8thth edition edition

Heritability of personality traitsHeritability of personality traitsHuman traits are Polygenic Human traits are Polygenic

More and more evidence is accumulating in More and more evidence is accumulating in support of the heritability of our traits and our support of the heritability of our traits and our aptitudes. How do we separate environmental aptitudes. How do we separate environmental from genetic effects? from genetic effects? The The twin study method. twin study method. Identical Identical (monozygotic) twins (MZ) share 100% of their (monozygotic) twins (MZ) share 100% of their genes. They are compared to fraternal genes. They are compared to fraternal (dizygotic) twins (DZ), who share Apr. 50% of (dizygotic) twins (DZ), who share Apr. 50% of their genes. When given a variety of their genes. When given a variety of personality tests, MZ twins’ scores are much personality tests, MZ twins’ scores are much more similar to each other than DZ twins’ more similar to each other than DZ twins’ scores. scores.

Identical twins share 100% of Identical twins share 100% of their genestheir genes

They are formed when a fertilized egg They are formed when a fertilized egg (zygote) is split , forming two identical (zygote) is split , forming two identical zygoteszygotes

Fraternal twins share about 50% of Fraternal twins share about 50% of their genes their genes

They are formed when two different eggs They are formed when two different eggs are fertilized by two different sperm cellsare fertilized by two different sperm cells

Other Methods to Study Heritability Other Methods to Study Heritability

Please note that the heritability of many Please note that the heritability of many psychiatric disorders has been establishedpsychiatric disorders has been establishedHuman characteristics are polygenetic, establish Human characteristics are polygenetic, establish by more than one gene, a fact which affects the by more than one gene, a fact which affects the study of heritability study of heritability Other procedures compare adopted children to Other procedures compare adopted children to their biological parents and adoptive parents, their biological parents and adoptive parents, finding more similarities between the adopted finding more similarities between the adopted children and their biological parents. children and their biological parents.

Heritability (cont-d) Heritability (cont-d)

Also, studies comparing MZ twins raised Also, studies comparing MZ twins raised together vs. MZ twins raised apart find that the together vs. MZ twins raised apart find that the identical twins raised apart are quite similar to identical twins raised apart are quite similar to each other, as much as identical twins raised each other, as much as identical twins raised together, suggesting a strong genetic influence together, suggesting a strong genetic influence on personality. on personality. In response, some critics suggest that identical In response, some critics suggest that identical twins may experience more “shared twins may experience more “shared environment” than fraternal twins, but this type environment” than fraternal twins, but this type of argument is rather weak.of argument is rather weak.

Introverts are NOT Shy Introverts are NOT Shy

They try to control their level of arousal They try to control their level of arousal

The study ofThe study of extraversion-extraversion-introversionintroversion

The genetic basis for this dimension has been The genetic basis for this dimension has been supported by large-scale twin studies in Sweden supported by large-scale twin studies in Sweden and Finland.and Finland. Physiologically, introversion has been Physiologically, introversion has been associated with high sensitivity to stimulationassociated with high sensitivity to stimulationA study in libraries found that introverted people A study in libraries found that introverted people preferred scheduled area to study in, while preferred scheduled area to study in, while extraverted preferred open, noisy areas.extraverted preferred open, noisy areas.This study supported the hypothesis of This study supported the hypothesis of sensitivity to stimulation. sensitivity to stimulation.

Who is Happier?Who is Happier?

Are extraverted people happier than Are extraverted people happier than introverted? Extraverted people introverted? Extraverted people experience higher levels of positive affect experience higher levels of positive affect than introverted. than introverted. Maybe because they have more friends, Maybe because they have more friends, and also they may be more sensitive than and also they may be more sensitive than introverts to information about rewards. introverts to information about rewards.

(cont-d) (cont-d)

Regarding happiness, researchers look at Regarding happiness, researchers look at happiness in terms of subjective well being, happiness in terms of subjective well being, which can be divided into positive and negative which can be divided into positive and negative affect.affect. Happiness is obtained by increasing positive Happiness is obtained by increasing positive affect and decreasing negative affect.affect and decreasing negative affect.Though extraverts experience more positive Though extraverts experience more positive affect than introverts, they are also more affect than introverts, they are also more impulsive, a factor that may get them into impulsive, a factor that may get them into trouble. They may experience more mood trouble. They may experience more mood swings than introverted.swings than introverted.

Evolutionary Theory and Mate selection Evolutionary Theory and Mate selection

Evolutionary psychology is interested in Evolutionary psychology is interested in understanding the biological basis for human understanding the biological basis for human behavior.behavior. Current human traits and attributes are seen as Current human traits and attributes are seen as evolving in us because they were useful for our evolving in us because they were useful for our survival in our prehistoric past. survival in our prehistoric past. The purpose of life is seen as the survival of the The purpose of life is seen as the survival of the species, the transmission of our genes to the species, the transmission of our genes to the next generation.next generation.

Parental Investment Parental Investment

Because of biological differences (“the cheap Because of biological differences (“the cheap sperm and precious egg”), men and women sperm and precious egg”), men and women have different parental investments in the have different parental investments in the transmission of their genes to their offspring, transmission of their genes to their offspring, and that is why they have evolved differently in and that is why they have evolved differently in terms of mate selection.terms of mate selection. Note “lonely hearts” studies. How do men and Note “lonely hearts” studies. How do men and women market themselves in order to attract a women market themselves in order to attract a mate, and what are they’re looking for in a mate, and what are they’re looking for in a potential partner?potential partner?

Gender Differences in Mate SelectionGender Differences in Mate Selection

Men prefer youth and beauty, because these Men prefer youth and beauty, because these indirectly mean health and fertility.indirectly mean health and fertility.Women prefer ambition, resources in a man.Women prefer ambition, resources in a man.Since their parental investment is larger than the Since their parental investment is larger than the man’s, they contribute their “precious egg”, man’s, they contribute their “precious egg”, women need to guarantee (not in the personal women need to guarantee (not in the personal sense, but in the sense of the species) that their sense, but in the sense of the species) that their relatively few offspring will be protected while relatively few offspring will be protected while they gestate, give birth, and nurse. they gestate, give birth, and nurse. Note cross-cultural studies showing that men in Note cross-cultural studies showing that men in different cultures all over the world prefer youth different cultures all over the world prefer youth and beauty in a mate. and beauty in a mate.

He wants youth and beauty she wants resources He wants youth and beauty she wants resources

She has youth and beauty he has moneyShe has youth and beauty he has money