Heredity and Temperament
Heredity and Traits
Evaluating Genetic Theories
|
|
|||||
Heredity and Temperament (p.42)
INTRODUCTION
Genetically based temperaments seem to influence later personality traits in predictable ways.
KEY CONCEPTS EXPLAINED
..Temperament
- Characteristic styles of responding appear so early in life they probably have
a genetic basis.
- Activity level, mood, responsiveness, soothability, and attention span.
- Examples
- Docile and sweet-nature = other people's kids.
- Irritable and cranky = your kids.
- Examples
The DNA in genes affect the structural and biochemical characteristics of the body, including the nervous system.
- Kagan's study of inhibited/uninhibited
temperament style in children.
- Styles defined:
- Inhibited temperament - shy, timid, react negatively to novel situations.
- Uninhibited - talkative and spontaneous.
- Biological connection:
- When placed in mildly stressful mental tasks, socially inhibited 5 year olds
show increased activity in the sympathetic branch of the autonomic nervous system
which is associated with physiological arouse
fast forward to a discussion
of the sympathetic nervous system in Chapter 4.
- Inhibition associated with allergies and blue eyes (also heredity).
- When placed in mildly stressful mental tasks, socially inhibited 5 year olds
show increased activity in the sympathetic branch of the autonomic nervous system
which is associated with physiological arouse
- Styles defined:
- Similar physiological attributes found in shy rhesus monkeys
- Temperament is usually stable over life.
- Consistency in temperament depends on how parents and others respond to an infant.
- Inhibited infant can overcome timidity if reared by a nurturant caregiver.
- However, an infant's temperament can also influence the parents' behavior.[It's true, mental illness is inherited: You get it from your kids!]
- Inhibited infant can overcome timidity if reared by a nurturant caregiver.
GLOSSARY
|
|
temperaments | ||
|
|
genes |
LINKS About Temperament
- www link: Academic overview of temperament.
|
|
Heredity and Traits (p.44)
INTRODUCTION
"Heritability" is a way to learn how much of a trait in a group is has a biological basis. Caution: This is a tough concept to master.
KEY CONCEPTS EXPLAINED
- Heritability is a statistical concept (we are in trouble all ready...).
- Official definition (read it ten times before it begins to make sense):
"A statistical estimate of the proportion of the total variance in some trait within a group that is attributable to genetic differences among the individuals within the group."
- Clarifying Example (we hope) --- Height is highly heritable, which means:
- In a group of well nourished people in the same community, most of the height
differences among them (variation) will be accounted for by their genetic differences
(because the environment is generally the same for the group).
- This estimate only applies to this group as a whole and not to any individual. One of the individuals may be tall because they were on a super nutritious diet most of their life.
- In a group of well nourished people in the same community, most of the height
differences among them (variation) will be accounted for by their genetic differences
(because the environment is generally the same for the group).
|
|
..Computing Heritability
More problems - You can't measure heritability directly It must be inferred by studying people whose genetic similarity is known.
- Families?
- Not good because they also share the same environment as well as genes.
- Not good because they also share the same environment as well as genes.
- Adopted Children
- While adopted children share genes with their biological parents, they grow up
in a different environment (of their adoptive parents).
- Can check to see if a trait compares more with their biological parents [nature]
than their adoptive parents [nurture]
- For example, the intelligence scores of adoptive children are more highly correlated
to their biological parents than their adoptive parents.
- While adopted children share genes with their biological parents, they grow up
in a different environment (of their adoptive parents).
- Identical Twins versus Fraternal
Twins
- Identical (monozygotic) twins come form the same fertilized egg and share the
same genes.
- Fraternal (dizygotic) twins come from two different fertilized eggs that just
happen to be "wombmates".... just siblings.
- Heritability can be assessed by comparing groups of identical twins with fraternal
twins.
- Assumption: If identical twins are more alike than fraternal twins in
a particular trait, the increased similarity must be genetic!
- Identical (monozygotic) twins come form the same fertilized egg and share the
same genes.
- The Separated Twin Strategy
- Avoids the problem that fraternal twins may not have the same kind of environment
as identical twins.
- Twins separated early in life and reared apart, share their genes but not their
environments.
- Therefore any similarity should be primarily genetic.
- Avoids the problem that fraternal twins may not have the same kind of environment
as identical twins.
GLOSSARY
|
|
heritability | ||
|
|
identical (monozygotic) twins | ||
|
|
fraternal (dizygotic) twins |
LINKS About Twin Studies
- www link: Overview of the Minnesota Twin Studies.
- www link: Brief review of twin studies in the media.
|
|
How Heritable are Personality Traits? [p.46]
- Heritability for most traits is between .40 and .60, which means:
Within a group of people, 40-60% of the variance of a specific trait is attributed to genetics.
- The only environmental contribution to personality differences comes from experiences not shared with family members --. shared environments and parental child rearing habits have no significant effect on adult personality traits [go figure].
|
|
Evaluating Genetic Theories [p.46]
- Measures of environmental factors are crude which leads to overestimating the
role of heredity.
- Separated identical twins are often raised in fairly similar settings....and
remember, the greater the similarity of the environment, the larger the heritability
estimate.
- The same data provide evidence for the importance of the environment.
- Heritability (the effect of genes) can change over time.
- Heritable traits can be modified
rewind to social inhibition
studies.
 |
| Next Topic - The Learning Tradition........................................Chapter Contents |