Cognitive Psychology, 2nd Ed.

Chapter 15Intelligence

General Intelligence

Intelligence Quotient (IQ): MA/CA x 100

General intelligence (g)Biological measures

-perceptual-motor RT -ERP complexity

General Intelligence

Fluid vs. Crystallized intelligenceGeneral fluid intelligence correlated with central executive functions of working memory.PET activation in left lateral prefrontal cortex for both spatial and verbal problem solving—indicative of central executive involvement.

Criticisms of g

Verbal IQ and Performance IQ are dissociated in aging.IQ tests measure linguistic, logical-mathematical, and spatial intelligence.Musical, bodily-kinesthetic, and intra- and inter-personal intelligence are ignored by IQ tests.

Nature vs. Nurture in IQ

Heritability (h2): Proportion of variance caused by genetic differences.Heritability: correlation between identical twins reared apart (r = h2).Heritability increases with age from .4 in childhood to .75 in late adolescence.Multiple genes, probabilistic effects

Nature vs. Nurture in IQ

Extent of parents talking with young children predicts verbal IQ.Deprivation, neglect, and abuse harm IQ but is there a threshold for normal development?

Nature vs. Nurture in IQ

Preschool programs (e.g., HeadStart) increases chances of finishing school.Deprivation, neglect, and abuse harm IQ, but is there a threshold for normal development?Flynn Effect: Increase in IQ in industrialized nations of 3 points per decade since 1940.

Sex Differences

Understanding effect size (d = mean difference divided by standard deviation)

d = .20 = smalld = .50 = medium

d = .80 = large

Sex Differences

Verbal ability: small advantage for females on some tests.Visuo-spatial ability: small to large advantage for males, depending on the specific test (e.g., mental rotation vs. spatial perception).

Sex Differences

Mathematical ability: small to medium advantage for males, because of larger male variability.Navigation: no sex advantage, but males use dead reckoning and females use landmarks.Motor Skills: male advantage in throwing and female advantage in manual control movements.

Reasons for Sex Differences

Social-cultural: males and females are socialized differently and conform to different cultural expectations. The degree of difference varies by culture.Biological: Natural selection in Upper Paleolithic era (40,000 to 60,000 years ago) may have favored verbal and fine motor control in females; navigation and throwing in males. Note brain lateralization in males.