Heritability Flashcards
Nature vs nurture intelligence
-IQ has a normal distribution in any given population, so some people are more intelligent than others
Approaches to nature vs nurture
-Biological and psychoanalytic (nature) to humanist and behaviorist (nurture)
Heritibility
-Variation of intelligence in a population can be attributed to genetic differences.
Genetic material
- What is genetic material?
- 98% of genetic material is shared (1-2% accounts for the variations)
- 97% of DNA is shared with chimps
Galton
-Suggested Darwin’s theory can be applied to intelligence which produces variations in intelligence e.g. superior traits = higher intelligence
Galton heredity genius study
- He looked at notable/successful individuals family histories to see if they were related to each other.
- Found that there were first degree relationships of successful individuals (50% of genes shared). Second degree (25%) and third degree (12.5%).
- This suggests genetics do influence intelligence, but some is also due to nurture (diet and education). Coined nature vs nurture.
Galtons twin studies
- Galton wanted to study how biological and environmental factors combined to make someone successful so looked at twins raised separately (same nature different nurture). Monozygotic are identical and dizygotic are non-identical.
- MZ twins reared together had the highest concordance rate of 86% with MZ twins not raised together having 76% this suggests that environmental factors are important but are not as important as genetic factors.
- This is supported as siblings reared together had concordance rates of 47% and those raised apart had 24%. Finally, cousins who are only third degree relatives only has 15% concordance rates.
Additive assumption
- Genetic and environmental factors combine to account for 100% variance
- Proposed V-E=G which does not work if both genetic and environmental influences is high so V=GxF should be used instead
External vs internal characteristics
- If parent and child look very similar there is likely high shared variance of external characteristics which may be the same for internal characteristics as physical characteristics are less influenced by environmental factors.
- Therefore, internal characteristics have lower shared variance.
Environmental influence on skills and abilities
-Shared interest transfer skills e.g. David Beckham teaches his son football skills
Adoption studies
- Eliminates genetics to focus on nurture
- Looked at biological parents’ vs their children who were given up for adoption, the adoptive family and the child’s abilities vs a control family.
- This found that biological families vs the children adopted out has the highest similarity at all ages. This was as high as the control families by the time they were 10. Adoptive families and children were the most dissimilar in verbal IQ.
Assortative thinking
-Heritability estimates are based on assumption of random mating. However, we are likely to be attracted to individuals that are similar to ourselves e.g. interests, attractiveness, personality, intelligence and physique
Types of environmental influences
-Biological, family, culture and school
Biological environmental factors influence intelligence
-Nutrition, substances e.g. alcohol, smoking etc. , Stopping breast feeding before 6 months linked to reduced verbal intelligence, 3-6 IQ points higher on vocab tests than non-breast fed.
Family environmental factors influence intelligence
- Shared and non-shared environments
- socioeconomic (adopted children had higher IQ if parents had high status jobs) -maternal education (strongest correlation predictor of childs IQ)
- birth order (first born has higher IQ).
