Transcript Nature, Nurture and Human Diversity

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
13.40
12.80
Sociability
15.24
14.60
Distress
10.08
9.72
Fearfulness
10.60
8.92
Anger
10.28
10.80
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