7 - Social Development parent offspring correlations have...

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Social Development - parent offspring correlations have been assumed by SSSM as evidence that parenting is important - cannot dissociate genetic and environmental contributions o shared home o shared genes Broad sense heritability - the amount of variation in population can attribute to genetic variation - cannot be applied to individual, only population measure - twin studies: Galton - monozygotic: one sperm one egg into a zygote, can then split into 2, 100% genes o dizygotic: two eggs each get fertilized, 50% genes in common - hair color, on average monozygotic have same hair color and dizygotic have different color - the trait is more similar in monozygotic then dizygotic, high heritability - if identical twins just as likely have different hair color as dizygotic, then heritability is low - graph: o individual differences tend to have pretty robust heritability scores Behavioural Genetic Approaches - partition variance into effects of o shared genes o shared environments o unique environments o shared genes and unique environment - typically effects of shared environment are tremendously small when effects of genes controlled Caveat - heritability estimates are environment specific - do NOT indicate a trait is X% genetic!! - heritability means the proportion of variance accounted for by genetic variation Group Socialization Theory - Judith Harris - proposes that after genes, next largest factor is peer group, not family o whats important is not parenting, but other experience outside the home (unshared environment) - e.g. language learning in immigrants o how we pronounce vary from experience we growing up o immigrants families: have an accent, but the kids don't - is peer learning an adaptation? - potential benefits of attending to peers rather than adults o younger individuals are the most innovative
o learning from peers increases variation in knowledge o parents may or may not be around in the future o parents and offspring often have conflicting interests - at this point theory is still contentious o large genetic contribution unequivocal o effects of shared and unshared environment awaiting study Group Socialization versus Parental Influence - Why not both? - Belsky argues for individual variation o About whats more adaptive - Differential susceptibility to rearing influence - unpredictable environments o attend less to parent, more to peers o more current practice beneficial to development - stable environments o use parents to direct development Differential Susceptibility - Caspi et al. (2002) found variation among Monoamine oxidase A genotypes, and propensity for antisocial behaviour following maltreatment - MAOA is important in neurotransmitter inactivation - Caspi et al. 2002 o Low MAOA and high MAOA o X-axis: childhood maltreatment: none, probable, severe o The probability that propensity of abuse related to probability of antisocial behavior o The variation of the environment really influence how they behave o Depending upon their genotype, individual variation o Highlights the importance of G X E interactions in development

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