Lecture 3 HEREDITY & THE ENVIRONMENT Visiting Assistant PROFESSOR YEE-SAN TEOH Department of Psychology National Taiwan University 1 Unless noted, the course materials are licensed under Creative Commons Attribution- NonCommercial-ShareAlike 2.5 Taiwan (CC BY-NC-SA 3.0)Attribution- NonCommercial-ShareAlike 2.5 Taiwan GENERAL PSYCHOLOGY

GENETIC FACTORS DETERMINE ONLY AN PERSON’S GENOTYPE (STARTING POINT), BUT GENES DO NOT DETERMINE HOW THE PERSON WILL END UP (PHENOTYPE) HEREDITY

W HAT IS THE GENOTYPE ? Genes inherited from parents Determines characteristics such as height, eye color No 2 people have exactly the same genotype, except identical twins Interacts with environment to produce phenotype Genotype

W HAT IS THE PHENOTYPE ? Genetic expression of individual’s physical & behavioral characteristics Observable & Measurable Study of phenotype helps us understand how genes & environment interact to influence development E.g. Motor abilities, intellectual skills, social behavior, personality traits Phenotype

THE GENOTYPE

THE PROCESS OF GENETIC TRANSMISSION WHERE THE GENES ARE Within each cell nucleus are chromosomes… On which genes containing the genetic code are located Chromosomes are bound by molecules of DNA.

THE PROCESS OF GENETIC TRANSMISSION MEIOSIS & SEXUAL REPRODUCTION Chromosome combinations occur during the formation of sperm and egg cells. Crossing over – exchange of genes on homologous chromosomes. Union of sperm and ovum = 23 male & 23 female chromosomes

THE PROCESS OF GENETIC TRANSMISSION MEIOSIS IN DEPTH Process of cell division. 23 chromosome pairs are split/halved. Halving enables union of sperm and egg. Result is 23 from the sperm combines with 23 from the egg to produce 46 for new human being.

HOW TRAITS ARE TRANSMITTED Since genes are located on chromosomes, they also come in pairs. Each gene occupies a position on each half of the chromosomal pair. 2 identical paired genes = homozygous 2 different paired genes = heterozygous A specific gene has alleles which produce variations of that gene. Wikispaces: KKPM

HOW TRAITS ARE TRANSMITTED Expressions of heterozygous combinations: 1. Dominant – one gene will govern outcome over other gene. E.g. Dimples vs no dimples 2. Recessive – allele that will affect phenotype only if it matches allele of partner gene (inherits same recessive allele from each parent). E.g. Baldness only if the gene pair is homozygous for the recessive trait.

HOW TRAITS ARE TRANSMITTED Expressions of heterozygous combinations: 3. Codominant – both genes affect phenotype. E.g. Blood type A + Blood type B = AB 4. Incomplete dominance – person with 2 different alleles will have a phenotype that’s intermediate. E.g. Serotonin transporter gene located on chromosome 17 can have alleles of different length, long allele has incomplete dominance over short.

P OLYGENIC I NHERITANCE The expression of some traits is controlled by more than one gene pair. Specific genetic patterns create a risk of developing a certain trait/disease. Example: Bipolar disorder and schizophrenia are much more likely if a person inherits a certain genetic pattern (not just one gene).

INTERACTION OF GENES Very few traits are specified by single genes – most traits depend on a combination of genes. Many behaviors or characteristics are influenced by multiple genes. A gene may influence more than one trait. Modifier genes affect the expression of other genes.

Online Mendelian Inheritance in Man (OMIM) Access the website for genetic database.

G ENE E XPRESSION Whether or not a gene will be active, depends on many factors that modify the biochemical environment inside the cell, turning genes “on” or “off”. What can alter gene expression?

1. E NVIRONMENT JUST OUTSIDE THE CELL … OTHER CELLS Gene

2. T IMING – SOME GENES ACTIVE EARLY VS LATE Childhood Adolescence Adulthood

C. O VERALL E NVIRONMENT & B EHAVIOR TEMPERATURE Weather or climate LEVEL OF STIMULATION Engaging vs Impoverished SOCIAL WORLD People you are with BEHAVIOR Exercise triggers body changes that activate gene GENE EXPRESSION

GENE-ENVIRONMENT INTERACTION IS BI-DRECTIONAL

Gene Expression Environment Experience Bidirectional Interaction between Genetic Factors and Context (a)Environment & experience impacts gene expression. (b)Genetic factors shape what person experiences.

T HE F IELD OF H UMAN B EHAVIOR G ENETICS Addresses the question of why humans develop in such diverse ways Calculation of heritability factors – estimates of contribution of heredity Studies the relative influences of heredity & environment Heritability factors vary according to environment HUMAN BEHAVIOR GENETICS

S OME MISCONCEPTIONS OF BEHAVIOR GENETICS ….(R UTTER, 1992; 2006) Genes limit potential. Strong genetic effects = insignificant environmental influences. Genetic influences diminish with age. Genes regulate only static characteristics.

HEREDITY & THE ENVIRONMENT

H OW DOES THE E NVIRONMENT INFLUENCE THE EXPRESSION OF GENES ? GENES ENVIRONMENT RANGE OF REACTION

RANGE OF REACTION (G OTTESMAN, 1963; P LOMIN, 1995) Heredity does not rigidly fix behavior. It establishes a range of possible developmental outcomes that may occur in response to different environments.

People with different genetic make-ups have different ranges of reaction. Range of reaction is particularly useful for understanding the variation in complex behaviors.

EXAMPLE: An enriched, stimulating environment can substantially improve a child’s intellectual ability. However, each child’s genotype determines the limits within which his/her ability will vary.

Source: From "Genetic Aspects of Intelligent Behavior " (p. 255), by I. I. Gottesman, in N. R. Ellis (Ed.), Handbook of mental deficiency: Psychological theory and research, 1963, New York: McGraw-Hill.

HEREDITY Environment A Outcome 1Outcome 2 Environment B Outcome 3

Aggressive Trait Violent Neighborhood Highly aggressive Sometimes aggressive Safe, classy nieghborhood Less aggressive/ controlled

AN IMPORTANT INFLUENCE ON THE GENE-ENVIRONMENT INTERACTION… Developmental Stage Critical periods: developmental stages where the impact of the environment on development is most significant. Example: Kids with PKU must be placed on a special diet (low in phenylalanine) immediately after birth to prevent mental retardation (Baumeister, 1967)

H OW DOES GENETIC MAKEUP SHAPE ONE ’ S ENVIRONMENT ? PASSIVE Parents with certain genetic predispositions create home environments that suit the inherited predispositions of their children. EVOCATIVE Children’s inherited tendencies/ behaviors evoke certain responses from others/social environment. ACTIVE Genetic makeup leads children to seek out experiences/ settings that are compatible with their inherited tendencies. Niche-Picking

EXAMPLES…. PASSIVE Intelligent, well educated parents provide home with books and stimulating conversation. Children’s inherited tendencies to be bright & learn are enhanced EVOCATIVE Babies with inborn tendencies to smile often will elicit positive response & stimulation from others (La Freniere, 2000) -> Babies’ genetic dispositions are magnified, smile more ACTIVE Niche-picking Children genetically predisposed to be extroverted actively seek company & join social activities. Extroversion is enhanced.

M ETHODS OF STUDYING INDIVIDUAL DIFFERENCES 1. Compare adopted children with their biological & adoptive parents. - Similarity to adoptive parents = environment. - Similarity to biological parents = shared genetic makeup. - Studies by Moffitt & Caspi, 2006; Rutter, 2006) - Comparison of biological siblings and adopted children in same home.

2. Compare identical and fraternal twins raised together in the same home. - If identical twins show more resemblance on a trait than fraternal twins do = genetic influence - If both identical and fraternal twins show similar strength of resemblance on a trait = environment

3. Compare shared & non-shared environments - Identical twins have more shared environments – (i) identical genes & inherited predispositions, (ii) similar treatment by parents, (iii) evoke similar responses from others, (iv) select more similar settings/companions/activities (Scarr, 1996). - Fraternal twins & siblings are more likely to have separate experiences and activities. - Towers et al similarity caused by shared home declines with age, more niche picking.

3 P RINCIPLES OF EVOLUTION OF BEHAVIOR THROUGH NATURAL SELECTION (a) There must be a variation among the individuals within a population. (b) Certain of the variants must survive and reproduce at higher rates than others. (c) The traits associated with this superior survival and reproduction must be passed from parents to offspring.

Genes Environment/Experience Evolution of Behavior

Copyrights PageWorkLicenseAuthor/Source 3 National Taiwan University YEE-SAN TEOH 4 National Taiwan University YEE-SAN TEOH 9 Wikispaces: KKPM d+Evolution 2012/03/17 visited 16 National Taiwan University YEE-SAN TEOH 17 National Taiwan University YEE-SAN TEOH 18 National Taiwan University YEE-SAN TEOH

Copyrights PageWorkLicenseAuthor/Source 20 National Taiwan University YEE-SAN TEOH 21 National Taiwan University YEE-SAN TEOH 24 National Taiwan University YEE-SAN TEOH 27 This graph is adapted from Gottesman, aL00elliaL00elli and out of copyrigh so belongs to public domain. 28 National Taiwan University YEE-SAN TEOH 29 National Taiwan University YEE-SAN TEOH 37 National Taiwan University YEE-SAN TEOH