Lecture 12.doc

October 15, 2009 Adolescent Development Most infants, soon after birth, show a preference for looking at faces over other complex stimuli. Preferring to look at faces helps facilitate the infant-caregiver bond and therefore helps ensure the infant?s survival. Preference for looking at faces can be described as Being strongly canalized ( Omir is doing very well in his Spanish class and seems to really enjoy it. Because of this, his parents have decided to take a family vacation to Spain. For Omir, this is an example of An Evocative G-E Correlation ( Who is inquiring about the reliability of a study? Dr. Nitty who wants to know whether a study of students? facial expressions during sex-ed class compared the facial expressions of others ( Behavioral Genetics Study of the relative contributions of nature and nurture to the great diversity that exists in human traits and abilities 2 basic questions How much is nature responsible for differences between individuals; how much is nurture responsible? How do heredity and environment work together in development of traits? How much? Heritability Estimate: measure extent to which individual differences in complex traits within a population are due to genetic factors Kinship studies: compare characteristics of family members; Twin studies: is trait more similar between identical twins than fraternal twins? How much? Concordance rates: % of instances in which both twins show a trait when it is present in one twin 100% identical twins = all heredity; no effect of environment Criticisms/Limitations Assumes additive effect Tend to overestimate role of heredity Identical twin environments are more similar than fraternal twin environments Does not reveal why/how the trait develops Does not suggest helpful interventions Can be misapplied to try to explain differences between races Ex. Intelligence How do Nature and Nurture work together? Reaction Range: each individual?s unique, genetically determined response to the environment Unique blends of heredity and environment lead to both similarities and differences in behavior Accounts for children?s varying responses to the same environment Canalization: Tendency of heredity to redistrict development of a trait to one or a few potential outcomes Strongly canalized traits develop similarly in a wide range of environments Ex. Walking is strongly canalized Weakly canalized traits show wider variation Ex. Personality, intelligence Canalization Why are some traits strongly canalized? Ensures survival Ensures everyone will develop certain species-typical skills under a wide range of rearing conditions Only extreme environmental conditions will affect their development Genetic Environmental Correlations Our genes influence the environments to which we are exposed 3 different types of G-E Correlations Passive Evocative Active G-E Correlations Passive: Parents create an environment compatible with their own heredity. If child is biologically related to parents, environment is related to (correlated to) child?s heredity Ex. Athletically inclined parents bring kids on hikes; enroll them in sports; play catch in backyard Evocative: Child behaves in ways consistent with their own heredity, evoking response from others (ex. Creating an environment) that in turn strengthens child?s original response Ex. Child sings well in music class (due to heredity) teacher notices and suggests she join chorus (evoked environment) She joins chorus and develops her singing voice (environment strengthens inherited ability) Active: Individual chooses environments that complement their genetic tendencies Ex. Innately athletically talented boy tries out for sports teams, develop skills Ex. Extroverted boy tries out for school musical, gets attention Ex. Intelligent girl joins chess club, exercises intellect G-E Correlations and Development Passive: most common in infancy/young children who do not have control over environment available to them Evocative: becomes more common as child matures; less later as Active Correlation becomes more prevalent; always possible Active: older children/adolescents/adults; can choose environments available to them One ? Way Street? Reaction range and Canalization: genes dictate how much the environment will influence the developmental of the trait Genes -----------------------------------------------------------------( Environment G-E Correlations: genes influence what environments we are exposed to Genes ---------------------------------------------------------------- ( Environment Epigenetic View Bi-directional Genes affect behaviors/traits & environmental experiences AND Environmental experiences & behaviors/traits can affect gene expression/activity Example of Envir (( Genes Boys with gene known to predispose them to higher aggression Typical environment: typical aggression No difference between boys with v without gene Severe abuse: higher aggression in boys with gene Boys without gene not as aggressive In other words, gene for higher aggression only affected behavior when exposed to severe abuse Aggression Example continued Environment -------------( Gene Abuse/not -----------------------------------------( gene expressed/not Note: Boys with gene were not more likely to experience abuse Difference in genes did not cause differences in environment