Psyc311: Developmental Psychology Chapter 2 Biological and Environmental Foundations

exercise What are some traits that you share with your family members? What are some traits that make you different from your family members? What factors (genes vs. environment) would you hold responsible for each of these traits? Which are most likely genetic? Which are most likely environmental?

nature vs. nurture How do we explain the tremendous variability in human traits and behaviors? It must be environment! Humans have only 3x more genes than fruit flies. Genes can’t explain behavioral flexibility Plasticity argues against innate wiring It must be genes! Genes have tremendous combitorial power Slight differences lead to large changes in behavior Cascades of change Innateness  pre-wiring Plasticity  re-wiring

nature vs. nurture Individual level: the extent to which any given child’s development the product of his/her genetic vs. environmental influences. Population level: the degree to which observed variation in particular traits (in a given population) is due to environmental or to genetic factors. Why does it matter?

? nature vs. nurture phenotype genotype The observable characteristics of a person, including appearance, personality, intelligence, and all other traits. phenotype ? An organism’s entire genetic inheritance or genetic potential. genotype

View #1 genotype phenotype

Not all variation in phenotypes can be explained by variation in genotypes. Scientists have studied thousands of twins, both monozygotic and dizygotic, raised together in the same home and raised separately in different homes

Notice that identical twins are not identical, (there is clear evidence for the effect of environment). Notice that DZ twins and regular siblings look the same. Why isn’t this surprising? Why is this surprising?

View #2 genotype environment phenotype

which contributes more?

which contributes more? Trait B High heritability (genes) High shared environmental variance High unshared (unique) environmental variance Trait A High heritability (genes) High shared environmental variance High unshared (unique) environmental variance Trait C  High heritability (genes) High shared environmental variance High unshared (unique) environmental variance

asking wrong question? Asking: which (genes or environment) contributes more to child’s phenotype. Is like asking: which (length or width) contributes more to the area of a rectangle? The correct question to ask is which contributes more to variation within a given group (of children and rectangles)?

range of reaction

environments influence genes Lots of genes are carried in a person’s genotype, but do not get expressed in their phenotype. "The phenotype is the unique consequence of a particular genotype developing in a particular environment" (Lewontin, 1982, pp. 22–23). So environment can influence Which genes get expressed How they get expressed

genes influence environment Passive genotype-environment correlation. Evocative genotype-environment correlation. Each child’s genes elicit other people’s responses, and these responses shape development. In other words, a child’s environment is partly the result of his or her genes. Active genotype-environment correlation. Children, adolescents, and especially adults choose environments that are compatible with their genes (called niche-picking), thus genetic influences in adulthood increase.

iclicker A child is exposed to music because her parents enjoy music and frequently have it playing in the background. A) passive B) evocative C) active A child is exposed to music because she has colic and will only quiet down and fall asleep when her parents put on music, so they frequently have music playing in the background. A) passive B) evocative C) active A child is exposed to music because she asks her parents if she can go to music camp for the summer. A) passive B) evocative C) active

View #3 genotype environment phenotype

epigenetic framework Can you think of protective and risk factors in your own life? neighborhood family SES culture Each layer can serve as either a protective or a risk factor for the developing child (and, at times, vice versa).

two important concepts Phenotypic plasticity: the degree to which an organism's phenotype is determined by its genotype. A phenotype is plastic if changes in the environment noticeably affect the physical properties of the organism. Low plasticity: the phenotype can be reliably predicted from the genotype The phenotype will express regardless of environmental variation. Genetic canalization: the extent to which an organism's phenotype allows conclusions about its genotype. A phenotype is canalized if changes in the genome do not noticeably affect the physical properties of the organism. High canalization: the genotype cannot be reliably predicted from the phenotype The phenotype will express regardless of genetic variation. Examples Language is low in plasticity and high in canalization. Eye color is low in canalization. Reading ability is high in plasticity.

exercise Name traits with low and high phenotypic plasticity Sensitivity to environment High sensitivity High plasticity Low sensitivity Low plasticity Name traits with low and high genetic canalization Sensitivity to genetic variation Low sensitivity High canalization High sensitivity Low canalization

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ADHD Genes Environment Commonly found in boys who have male relatives with the same problem Heritability rate 60-91% Generates overactivity across environmental contexts Home as well as school Typically calmed by stimulants Ritalin, Adderall, and even coffee Environment The rapid increase in ADHD from 1 to 5 % of all U.S. children in the past 50 years Many environmental factors correlated with ADHD crowded homes, television, lead, food additives, rigid teaching, lack of sleep

ADHD

alcohol and drug addiction Genes Inherited biochemistry makes people vulnerable to various additions Fewer dopamine receptors People with high anxiety or quick tempers more likely to drink Environment Environments contribute to the likelihood that an addiction will form College Culture Gender – genetic or environmental?

nearsightedness Environment also influences nearsightedness Nearsightedness is a symptom in more than 150 genetic syndromes Commonly inherited trait Environment also influences nearsightedness diet is deficient of vitamin A large quantities of close-in vision (reading books/computer screens)

Type 2 diabetes Rapid increase due to environmental changes What are some of these changes? Also a genetic pre-disposition Only some people vulnerable to the risk factors

IQ Interesting gene-environment interaction: Fatty acids DHA and ARA promote neuronal growth/connectivity Breast milk is rich in DHA and ARA Absence of breast milk may negatively effect IQ Certain genes play crucial role in metabolism of these fatty acids Babies that have these genes benefit from breast milk; others don’t.

political orientation How could political orientation be genetic?! Liberal vs. conservative ideology Instinctive emotional response