Nature, Nurture and Human Diversity: temperament and heritability

How stability of our temperament illustrates the influence of heredity on development Temperament: characteristic emotional excitability and intensity –Relaxed and cheerful v. tense and irritable Ex: emotionally intense preschoolers tend to be relatively intense young adults Compared with fraternal twins, identical twins have more similar temperaments

What is heritability and interaction of gene environment on specific traits? Heritability: extent to which variation among members of a group can be attributed to genes –Heritability of intelligence = 50% Does not = 50% genetic Does equal ability to attribute genetic influence on 50% of the observed variation Conclusion?

Self-regulation Genes are self-regulating –Conclusion – they react differently in different environments We are all products of interactions –Genetic predispositions and surrounding environments

Interactions Ex. 1: Stressful environments can trigger genes that affect production of neurotransmitters that underlie depression Ex 2: Breastfeeding boosts later intelligence only for the 90% of infants with a gene that assists in breaking down fatty acids present in human milk Ex. 3: A baby who is genetically predisposed to be social and easy going may, in contrast to another who is less so, attract more affectionate and stimulating care and thus develop into a warmer and more outgoing person

Buss and Plomin’s EAS Temperament Survey Measures broad personality dispositions: –Activity: person’s energy output –Emotionality: intensity of emotional reactions –Sociability: tendency to affiliate and interact

How to score Reverse the number placed in front of items 6, 18, and 19 (5=1, 4=2, 3=3…) Add scores for items 2, 7, 10, and 17 –Activity Add scores for 1, 6, 15, and 20 –Sociability Add scores for 4, 9, 11, and 16 –Distress emotionality Add scores for 3, 12, 14, and 19 –Fearful emotionality Add scores for 5, 8, 13, and 18 –Anger emotionality

Women Men Activity Sociability Distress Fearfulness Anger

Findings Buss and Plomin –Temperament is largely inherited –Identical twins show more similar temperaments Correlations for identical were.63,.62, and.53 Correlations for fraternal were.12, -.13, and -.03

Conclusions Heredity may point personality in a certain directions – but the direction is influenced by environment –Highly emotional child is more likely than a less emotional one to become aggressive, parents who reward problem-solving skills over expression of anger may shape the aggressive child into a cooperative, altruistic adult Infants are NOT blank slates on which parents may “write” the child’s personality