Is Intelligence Neurologically
Measurable?
Brain size correlation to intelligence: +.33
What does this mean?
Portion sizes vary as well
Einstein had abnormally large parietal lobes
Environmental experiences impact
Rat neural connections example
Highly educated people die with 17% more
synapses than counterparts
Other Environmental
Influences
 Infants who suffer from extreme malnutrition during
infancy average 20 I.Q. points lower than other children
(Stock and Smythe, 1963)
 Toxins in the environment such as lead found in some
paints are associated with reduced I.Q. (Needleman,
1990)
 Intelligence declines with family size; the fewer children
there are the smarter you are likely to be (Zajonc, 1975)
 Intelligence declines with birth order; first-borns tend to
be brighter (Zajonc, 1975)
 I.Q. is negatively correlated with family risk factors, such
as social class or absence of father figure (1989)
Are There Multiple
Intelligences?
 Social Intelligence
 the know-how involved in
comprehending social situations and
managing oneself successfully
 Emotional Intelligence
 ability to perceive, express, understand,
and regulate emotions
Brain Function and
Intelligence
 Correlation
between fast
perceptual speed
and general
intelligence
 People who can
perceive the
stimulus very
quickly tend to
score somewhat
higher on
intelligence tests
Stimulus
Mask
Question: Long side on left or right?
Neurological Speed
Correlation between intelligence and
neurological processing
Assessing Intelligence
 Aptitude Test
 a test designed to
predict a person’s
future performance
 aptitude is the capacity
to learn
 Achievement Test
 a test designed to assess what a person
has learned (ex: unit exams, driver’s test)
Assessing Intelligence
 Wechsler Adult Intelligence Scale (WAIS)
 most widely used intelligence test
 subtests
 verbal
 performance (nonverbal)
Assessing Intelligence:
Sample Items from the WAIS
VERBAL
PERFORMANCE
General Information
Similarities
Arithmetic Reasoning
Vocabulary
Comprehension
Digit Span
Picture Completion
Picture Arrangement
Block Design
Object Assembly
Digit-Symbol Substitution
From Thorndike and Hagen, 1977
Assessing Intelligence
 Standardization
 defining meaningful scores by comparison
with the performance of a pretested
“standardization group”
 Normal Curve
 the symmetrical bell-shaped curve that
describes the distribution of many physical
and psychological attributes
 most scores fall near the average, and fewer
and fewer scores lie near the extremes
The Normal Curve
Getting Smarter?
Flynn
Effect:
IQ scores
going up
about 3 points
per decade
Assessing Intelligence
 Reliability
 the extent to which a test yields consistent
results
 assessed by consistency of scores on:
 two halves of the test
 alternate forms of the test
 retesting
 Validity
 the extent to which a test measures or
predicts what it is supposed to
Assessing Intelligence
 Content Validity
 the extent to which a test samples the
behavior that is of interest
 driving test that samples driving tasks
 Criterion
 behavior (such as college grades) that a
test (such as the SAT) is designed to
predict
 the measure used in defining whether
the test has predictive validity
Assessing Intelligence
 Predictive Validity
 success with which a test predicts the
behavior it is designed to predict
 assessed by computing the correlation
between test scores and the criterion
behavior
 also called criterion-related validity
Assessing Intelligence
Football 10
linemen’s 9
success
Greater correlation
over broad range
of body weights
8
7
6
5
Little correlation within
restricted
range
4
3
2
1
0
180
250
290
Body weight in pounds
 As the range of
data under
consideration
narrows, its
predictive
power
diminishes
The Dynamics of
Intelligence
 Is intelligence stable across the
lifespan or does it change?
Intelligence
test scores
don’t stabilize
until about age
7; after that
about a +.66
correlation over
time
The Dynamics of
Intelligence
 Extremes of Intelligence
 Mental Retardation
 a condition of limited mental ability
 indicated by an intelligence score below 70
 produces difficulty in adapting to the demands
of life
 varies from mild to profound
 Down Syndrome
 retardation and associated physical disorders
caused by an extra chromosome in one’s
genetic makeup
The Dynamics of
Intelligence
Tracking
From early age students are often tracked
into “gifted” programs and “remedial”
programs… what’s a potential problem
with this?
Self-Fulfilling Prophecy
Genetic Influences
 The most
genetically
similar
people have
the most
similar
scores
Genetic Influences
Environmental
Influences
 The Schooling Effect
Intelligence scores drop over the summer
when students are not in school
Group Differences
 Average IQ scores by racial groups
 Whites: Roughly 100
 Blacks: Roughly 85
 Hispanics: Roughly 92/93
 Differences are diminishing over time
 What explains these differences?
Group Differences
Gender Differences
Girls score higher on:
Spelling
Verbal Ability
Nonverbal Memory
Sensation (more sensitive)
Detecting Emotion
Boys outnumber girls in
special education, talk
later, stutter more often
Girls now match or
surpass boys at math
The Question of
Bias
 Are intelligence tests biased?
 Depends on definition of “biased,” but…
 Yes, often due to CULTURAL BIAS
 Chitling Test, Australian Aboriginie Test examples
 Stereotype Threat
 A self-confirming concern that one
will be evaluated based on a
negative stereotype
 Example: Women score higher on math tests when no male
test-takers are in the room
Group Differences
 Stereotype Threat
 A self-confirming concern that one
will be evaluated based on a
negative stereotype