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 SpeedCorrelation 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

From Thorndike and Hagen, 1977

VERBAL

General Information Similarities Arithmetic ReasoningVocabularyComprehensionDigit Span

PERFORMANCE

Picture Completion Picture ArrangementBlock DesignObject AssemblyDigit-Symbol Substitution

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?

FlynnEffect: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

As the range of data under consideration narrows, its predictive power diminishes

Greater correlationover broad rangeof body weights

10

9

8

7

6

5

4

3

2

1

0

Little corre-lation withinrestricted

range

Football linemen’s

success

Body weight in pounds180 250 290

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 EffectThe 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:

SpellingVerbal AbilityNonverbal MemorySensation (more sensitive)Detecting Emotion

Boys outnumber girls in special education, talklater, stutter more often

Girls now match orsurpass 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 ThreatA 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 ThreatA self-confirming concern that one will be evaluated based on a negative stereotype