PT 4

What Influences Intelligence?

Nature or Nurture?

• Intelligence comes from innate characteristics (genes) and unique experiences (environment)

What is Evolution?

Evolution: A gradual change in our heritable traits within a population of individuals overtime

What is Natural Selection?

Natural Selection: the process whereby the genes that produce traits that increase the likelihood of survival and reproduction are maintained in the gene pool and become more common in population over time.

• What makes evolution occur?

• Oversimplified as the survival of the fittest

Important Concepts

• Phenotype: The observable expression of a trait

  • produced by underlying genetic factors, environmental factors, and the interaction between the two

• Heritability: How much of the variation in a characteristic within a population can be attributed to genetic differences within that population?

• Heritability Coefficient: estimate of how much of a characteristic is due to genetic factors

  • aka: heritability estimate — actual calculation

  • similar

• Concordance rate: rate of co-occurrence of a characteristic among individuals

  • two individuals having same diagnosis

  • ex) if twin A has x, how likely is twin B to have it as well?

  • Higher rate with increasing relatedness, possible genetic contribution

Environment or Genetics?

• If two organisms are raised in the exact same environment, but they are displaying different phenotypes/traits, then there must be genetic differences

• if we have two organisms that are genetically identical but show different phenotypes/traits if raised in different environments, then the environment must have an influence on that trait

Genetic Relatedness

• Parent and Child = 50%

• Grandparent and grandchild = 25%

• Between siblings = 50%

• Between twins

  • monozygotic (identical) = 100%

  • dizygotic (fraternal) = 50%

Family Studies and Adoption Studies

Family Studies

• Ask if traits are more common within a family vs the rest of the population

• Track patterns of inheritance across generations

Adoption Studies

• Share genes, but not environment, with biological relatives

• Shared environment, but not genes, with adopted relatives

Twin Studies

• Separates genetic and environmental influences

• Agreement between adoption and twin studies increases confidence in results

• Francis Galton - conducted the first twin study in Britain in 1875

• If there is mainly a genetic contribution:

  • MZ twins should resemble more than DZ twins - ex) height

• If there is mainly an environmental contribution

  • MZ twins and DZ twins should resemble each other equally - ex) religion

PT 5

Genes are not deterministic!

• As always, remember that genes are not destiny

• Very very few genes are deterministic

• Genes provide a predisposition towards a trait, but the environment also plays a role

Reaction Range

Reaction Range: Range of possibilities that genetic code allows

• Inherit range for potential genetic expression

• Environmental effects determine where person falls within that range

Non Genetic Component?

• Shared Environment: Those environmental factors that all relevant members of a household experience

• Nonshared Environment: Those environmental factors that all relevant members of a household do not experience

Age and Intelligence and Intelligence Across Time

• Heritability of intelligence generally increases with age of sample

  • When younger, there is less differences in IQ due to genetics, because as babies and toddler’s, a majority of our environment is our homes, so that main factor in differences would be our environment. As we get older and go to school, in a more shared environment with our peers, the IQ differences are more attributable to genetic differences.

• Intelligence tends to decline when we get older

  • fluid intelligence declines more rapidly

  • If we continue to stimulate our brains in old age, it could be protective from that decline

Standardization - Bell Curve of Intelligence

• IQ Tests have been standardized - calculations that happen behind the scenes have been set up in a controlled way so that when an intelligence test is conducted in a population, the average score of that population will be 100

• There is a standardized curve that has a known distribution

  • distribution of scores is organized and set up so that there is an even curve in the graphs

The Flynn Effect

• Product of not standardizing tests every year - keep a test from the past and use that as the standard

• Intelligence quotients seem to change over time

• Intelligence scores are rising by .3% every year

• Most likely due to a combination of factors

  • overall improvement in nutrition and medical care

  • improvements in education

  • Increased environmental complexity via technology

Self Enhancement Bias

Self Enhancement Bias: tendency to judge one’s performance as better than the average without any evidence of special expertise or training

• the idea that you are better than everyone else

Socioeconomic Status and Intelligence

• One of the best predictors of intelligence

  • Low SES may impair brain development

  • High SES families are more likely to provide intellectual stimulation

Education and Intelligence

• Correlation between formal education and intelligence is large (r= 0.55 to 0.90)

  • smart people tend to stay in school, and school makes you smarter

• Education may improve test-taking ability rather than general cognitive ability

Sex Differences in Cognitive Abilities

• Women are better at perceptual speed and language and verbal fluency,

• Men are better that spatial tasks, moving or manipulating an object, awareness of their own body, motor skills

• Women and men use different type of cues in terms of navigation, men are global while women are local

Biases in Intelligence Tests

• Outcome bias - refers to the extent that a test underestimates a person’s true intellectual ability

• Predictive Bias - occurs if the test successfully predicts criterion measures, such as school or job performance, for some groups but not others

Stereotype Threat

Stereotype Threat: Fear of confirming negative beliefs that others hold about your group may actually lead to poor performance

• self fulfilling prophecy

Example: mathematical ability across gender