Intelligence

Psychologists define intelligence testing as a method for assessing an individual’s mental aptitudes and comparing them with others using numerical scores.

ASSESSING INTELLIGENCE

Cousin of Charles Darwin.

Assessed reaction time, sensory acuity, muscular power, and body proportion of more than 10,000

visitors of the 1884 London Exposition.

He was unable to show correlations but he did give us

some statistical techniques that are still in use and the phrase “nature

and nurture.”

Why he did it: Wanted to measure “natural

ability” and encourage those of high ability to mate with one

another.

Francis Galton

France instated compulsory education for all children around the turn of the twentieth century and many seemed unable to do

the work. Rather than rely on the subjective reports of teachers,

the French government commissioned Binet to devise

an objective assessment of intelligence.

Why he did it: To identify students who

needed special help in coping with the school curriculum.

Alfred Binet

• All children follow the same intellectual development but some develop more rapidly• Dull (younger) vs. Bright (older) children

• Mental Age is the chronological age typical of a given level of performance

• The average 9 year old has a mental age of 9.• Below-average mental age would be a 9-year-old who

persons at the level typical of 7-year-olds.

Binet‐Simon Scale

• Led to the development of reasoning & problem solving questions that might predict school achievement.

• He hoped it would improve children’s education but feared it would be used to label children and limit their opportunities.

• For low-scoring children, he recommended “mental orthopedics” (exercises) that would help develop their attention span and self-discipline.

Binet‐Simon Scale

Coming to America

• The idea of IQ testing became popular in America for three reasons:• A huge increase in immigration• New laws requiring universal education• Military assessing new recruits for WWI

• It created an inexpensive and objective way to separate those who could benefit from education or military leadership training and those who needed assistance.

Downside of IQ Testing

• Despite its utility, IQ testing had a big downside. Tests ended up reinforcing prevailing prejudices about race and gender.

• They ignored the fact that environmental disadvantages limit the full development of people’s intellectual abilities.

Lewis Terman

In the US, Lewis Terman(Stanford University) adapted Binet’s test for American school children and named the test the Stanford-Binet Test.

He added items, established new age norms, and extended the upper end of the test’s range from teenagers to “superior adults.”

Binet did not believe his intelligence test measured inborn intelligence, but Terman believed his tests revealed the intelligence with which a person was born.

Why he did it:Terman believed in eugenicsEugenics: a social movement aimed at improving the human species through selective breeding…promoted higher reproduction rates of people with ‘superior’ traits, and aimed to reduce reproduction rates of people with ‘inferior’ traits. Resulted in legislation in many states that led to the forced sterilization of more tan 64,000 people (typically the disabled, poor, uneducated, and minority populations)

In particular, California’s program was so robust that the Nazi’s turned to California for advice in perfecting their own efforts. Hitler proudly admitted to following the laws of several American states that allowed for the prevention of reproduction of the “unfit” (Black 2003).

Lewis Terman

• German psychologist, William Stern, createdthe Intelligence Quotient (IQ)

• This original formula worked well for children but not adults

• Modern tests don’t compute IQ even though the expression has stuck• They represent the test-taker’s performance relative to

the average performance of others the same age• Average = 100• 2/3 score between 85-115

William Stern

Misuse and Abuse

• Intelligence testing has been used to encourage only smart and fit people to reproduce. Terman envisioned that the use of intelligence tests would ultimately result in curtailing the reproduction of feeble-mindedness and in the elimination of an enormous amount of crime, pauperism, and industrial inefficiency.

• Intelligence tests were also given to waves of immigrants and, obviously, since they did not speak the language or understand the culture and customs, they had low scores and were thought to be unintelligent. This led to the 1924 immigration law reducing the number of Southern and Eastern European immigrants that could enter the United States.

Achievement Tests• Intended to measure what you have learned• Examples: AP, final exams

Aptitude Tests• Intended to predict a person’s future performance• Aptitude = the capacity to learn• Examples: SAT

MODERN TESTS

Wechsler developed the Wechsler Adult Intelligence Scale (WAIS)and later the Wechsler Intelligence Scale for Children (WISC), an intelligence test for school-aged children. The most widely used individual intelligence today.

David Wechsler

WAIS measures overall intelligence and 11 other aspects related to intelligence that are designed to assess clinical

and educational problems.

For a psychological test to be acceptable it must fulfill the following three criteria:

StandardizationReliabilityValidity

TEST CONSTRUCTION

Standardizing a test involves defining uniform testing procedures and administering the test to a representative sample of future test takers in order to establish a basis

for meaningful comparison.

The AP® Psychology Exam is designed to assess your performance in a college-level introduction to psychology course; thus, it should be standardized using a population of freshman or sophomore college students taking introduction to

psychology in college. The same test should be given to the college students and the AP® students and the scores can then be meaningfully compared.

Standardization

Standardized tests establish a normal distribution of scores on a tested population in a bell‐shaped 

pattern called the normal curve.

Normal Curve

The Flynn effect shows that intelligence test performance has been improving since the 1930s. The cause has been a mystery, but people think it may be due partly to better nutrition, more

education, more stimulating environments, less childhood diseases, and/or smaller families.

Flynn Effect (New Zealand researcher James Flynn who first calculated the phenomenon)

A test is reliablewhen it yields consistent results. To establish reliability researchers establish different 

procedures:

1. Split‐Half Reliability: Dividing the test into two equal halves and assessing how consistent the scores are.

2. Test‐Retest Reliability: Using the same test on two occasions to measure consistency.

Reliability

The higher the correlation between the test‐rest and split‐half scores, the higher the test’s reliability.The Stanford‐Binet, the WAIS, and the WISC all 

have reliabilities of about +.9 which is very high. In other words, when retested, people’s scores generally match their first score closely.

Reliability

Reliability of a test does not ensure validity. Validity of a test refers to the extent to which the test 

actually measures or predicts what it is supposed to.

1. Content Validity: Refers to the extent a test measures a particular behavior, criterion, or trait.

2. Predictive Validity: Refers to the function of a test in predicting a particular behavior, criterion, or trait.

Validity

Are general aptitude tests as predictive as they are reliable?Academic aptitude tests are reasonably good predictors of achievement for children ages 6 to 12 (about +.6 correlation between intelligence score and school performance). Even 

closer reliability with achievement tests (+.81).

The SAT is less successful in predicting first‐year college grades (less than +.5). The GRE correlation is only +.4 

(modest but still significant).

When we validate w test using a wide range of people but then use it with a restricted range of people, it loses much of 

its predictive validity.

Validity

How stable are intelligence scores over the life span?

Cross‐Sectional Studies: Researchers compared people of various ages at one point in time and have found that older adults give fewer correct answers on intelligence tests than do younger adults. Wechsler concluded that the decline of mental ability with age is part of the general aging process 

of the organism as a whole. 

Stability or Change

How stable are intelligence scores over the life span?

Longitudinal Studies: After colleges in the 1920s began giving intelligence tests to entering students, psychologists began retesting the same cohort over a period of years.They found that until late in life, intelligence remained 

stable, and on some tests it even increased.Essentially the cross‐sectional studies were comparing 

people of different ages, but also different eras, education levels, family size, etc. and therefore the myth that 

intelligence sharply declines with age was laid to rest.

Stability or Change

How stable are intelligence scores over the life span?

The answer depends on what is assessed and how it is assessed.

Crystallized intelligence—our accumulated knowledge as reflected in vocabulary and analogies tests— increases up to 

old age. Fluid intelligence—our ability to reason speedily and 

abstractly as when solving novel logic problems— decreases beginning in the twenties and thirties, slowly up to age 75 or 

so, then more rapidly, especially after age 85.

Stability or Change

How stable are intelligence scores over the life span?

Stability or Change

We lose recall memory and processing speed, but we gain vocabulary knowledge. Our decisions become less distorted by negative emotions such as anxiety, depression, and anger. Despite their lesser fluid intelligence, older adults show increased reasoning, such as taking multiple perspectives, appreciating knowledge limits, and offering helpful wisdom in times of social conflict.

A valid intelligence test divides two groups of people into two extremes: the intellectually disabled (IQ 70) and individuals with high intelligence (IQ 135). These two 

groups are significantly different.

Extremes of Intelligence

Today this is referred to as intellectual disability

In addition to an IQ of 70 or below, they also have difficulty in adapting to the demands of life with limitations in the 

following areas.

Conceptual SkillsSocial Skills

Practical Skills

Intellectual disability is a developmental condition that is apparent before age 18, sometimes with a known physical cause. EXAMPLE: people with Down Syndrome have an 

extra chromosome 21 in their genetic makeup.

Intellectually Disabled

These individuals required constant supervision a few decades ago, but with a supportive family environment and 

special education they can now care for themselves.

Intellectually Disabled

Contrary to popular belief, people with high  intelligence test scores tend to be healthy, well 

adjusted, and unusually successful academically.   

High Intelligence

The Termites were the people in Lewis Terman’sstudy group over seven decades. These were high-scoring children who he followed longitudinally. Most of the Termites went on to attain high levels of education and became doctors, lawyers, and professors, for example.

A recent study of precocious youths who aced the math SAT exam at age 13 were at age 33 twice as likely to have patents as were those in the bottom quarter of the top 1 percent. Compared with the math aces, verbal whiz kids were more likely to have become humanities professors or written a novel.

http://www.intelligencetest.com/ Do not show your results to anyone!!! Take this intelligence test and write a

reflection to discuss the results of your IQ test.

HERITABILITY: 

The variation in intelligence test scores attributable to genetics. We credit heredity 

with 50%‐80% of the variation in intelligence. 

It pertains only to why people differ from one another, not to the individual.

Genetic Influences

Genetic InfluencesStudies of twins, family members, and adopted children together support the idea that there is a significant genetic contribution to intelligence.

Adoption StudiesAdopted children show a marginal correlation in 

verbal ability to their adopted parents.

Environmental InfluencesStudies of twins and adopted children also show 

the following:1. Fraternal twins raised together tend to show similarity 

in intelligence scores.2. Identical twins raised apart show slightly less similarity 

in their intelligence scores.3. During childhood, the intelligence test scores of 

adoptive siblings correlate modestly. Over time, adopted children accumulate experience in their differing adoptive families; however, genetic influences become more apparent as we accumulate life experience so mental similarities between adopted children and their adoptive families wane with age.

Early Intervention EffectsEarly neglect from caregivers leads children to develop a lack of personal control over the 

environment, and it impoverishes their intelligence.

Romanian orphans with minimalhuman interaction are delayed in 

their development.

Hunt (1982) used tutored human enrichment to train care-givers in a destitute Iranian orphanage where children received little care. By 22 months, the infants could now name objects and were so charming that most were adopted.

Although malnutrition, sensory deprivation, and social isolation can slow down normal brain development, there is no environmental recipe for fast forwarding a normal infant into a genius.

Schooling EffectsSchooling is an experience that pays dividends, which is reflected in intelligence scores. Increased schooling correlates with higher intelligence scores.

To increase readiness for schoolwork,projects like Head Start facilitate leaning.

Schooling EffectsCarol Dweck has been promoting the idea of a “growth mindset”. If one believes that intelligence cannot be changed, one may not further their education or take opportunities for 

cognitive growth. Having a growth mindset and believing intelligence is changeable result in a focus on learning and 

growing.

Ethnic Similarities and Differences

Racial groups differ in their average intelligence scores. Also, high-scoring people (and groups) are more likely to attain high levels of education and income. Group differences in a heritable trait may be entirely environmental, however.

Racial (Group) DifferencesIf we look at racial differences, white Americans score higher in average intelligence than black 

Americans (Avery and others, 1994). European New Zealanders score higher than native New 

Zealanders (Braden, 1994).

White‐Americans Black‐Americans

Average IQ = 100 Average IQ = 85

Hispanic Americans

Environmental EffectsDifferences in intelligence among these groups are largely environmental, as if one environment is more fertile in developing these abilities than the 

other.  

Reasons Why Environment Affects Intelligence1. Races are remarkably alike genetically. 2. Race is a social category.3. Asian students outperform North American 

students on math achievement and aptitude tests.4. Today’s better prepared populations would 

outperform populations of the 1930s on intelligence tests. 

5. White and black infants tend to score equally well on tests predicting future intelligence.

6. Different ethnic groups have experienced periods of remarkable achievement in different eras.

Gender Similarities and Differences

In the 1932 testing of the Scottish children, boys’ and girls’ average intelligence test scores were the same. Generally speaking, there are typically more differences among girls and among boys than there are between boys and girls, but researchers and the general public find sex differences more intriguing to focus on. Some studies have shown girls to have stronger spelling scores and higher verbal fluency and boys to have higher spatial abilities and math 

computation skills.

Gender Similarities and DifferencesThere are seven ways in which males and females 

differ in various abilities.

1. Girls are better spellers

2. Girls are verbally fluent and have large vocabularies

3. Girls are better at locating objects

4. Girls are more sensitive to touch, taste, and color

5. Boys outnumber girls in counts of underachievement

6. Boys outperform girls at math problem solving, but under perform at math computation

7. Women detect emotions more easily than men do