Cognitive Psychology, 2nd Ed.
Chapter 15
Intelligence
General Intelligence
Intelligence Quotient (IQ):
MA/CA x 100
General intelligence (g)
Biological measures
-perceptual-motor RT
-ERP complexity
General Intelligence
Fluid vs. Crystallized intelligence
General 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, logicalmathematical, and spatial intelligence.
Musical, bodily-kinesthetic, and intraand 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 = small
d = .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.