Intelligence Testing in Psychology

Editorial Note: This chapter examines the complex and often troubling history of intelligence testing, including its deep connections to the eugenics movement. While intelligence tests have legitimate scientific and educational applications, their historical misuse has caused significant harm to marginalized communities. This content is presented for educational purposes to understand both the scientific development and social consequences of psychological testing.

This chapter covers the development of intelligence tests, examples of early intelligence tests and how they work, discussion of the concept of intelligence in relation to these tests, and historical examples of how the tests were used in the context of the eugenics movement.

Key Questions

How did intelligence testing develop as a scientific discipline?
What were the motivations behind early intelligence tests?
How did eugenics ideology influence the development and application of mental testing?
What were the social consequences of intelligence testing in education, military, and mental health?
How did marginalized communities respond to discriminatory testing practices?

The Intelligence Test Race

The Stanford-Binet test was among the first intelligence tests to be widely adopted and used in America. Alfred Binet (1857-1911) was a French psychologist who published the Binet-Simon test (with his student Theodore Simon) in 1905, which described revised intelligence tests Binet was working on for over a decade prior. Lewis Terman was an American psychologist at Stanford University, who helped popularize Binet's test in America, hence Stanford-Binet.

It is convenient to start with the Stanford-Binet test, because Terman and Binet represent somewhat dueling progressive notions (for the time) about how psychological science could and should be used to improve society. These dueling notions involve the nature/nurture debate about the heritability and fixed or flexible nature of mental abilities; and the implications of that debate for enacting social policy.

Terman's Eugenic Vision

In the early 1900s, countries were finding ways to respond to social issues (crime, education, mental healthcare) with social institutions and policies. The eugenics movement, of which Terman was a strong proponent, billed itself as a progressive movement capable of fixing society's ailments. From Terman's perspective, intelligence tests would have obvious benefits for negative and positive eugenics policies:

Negative Eugenics Applications:

Mental testing would make institutionalization more effective at segregating "unwanted" people from society
Terman predicted that "intelligence tests will bring tens of thousands of these high-grade defectives under the surveillance and protection of society"
He believed this would "ultimately result in curtailing the reproduction of feeble-mindedness and in the elimination of an enormous amount of crime, pauperism, and industrial inefficiency"

Positive Eugenics Applications:

Intelligence testing could identify hidden geniuses and groom them to become national leaders
Terman wrote: "The number of children with very superior ability is approximately as great as the number of feeble-minded. The future welfare of the country hinges, in no small degree, upon the right education of these superior children."

Binet's Alternative Approach

Binet did not presume that mental abilities were fixed or inherited, and he argued that presumptions about human intelligence were premature in the absence of rigorous tests providing objective evidence. Binet was hired by the French government to address pressing issues in education.

Binet's Concerns:

Without objective mental tests, French schoolchildren were already being divided into "normal" and "defective" categories
Existing methods for deciding children's fate were deeply flawed, arbitrary, and open to bias
Some normal children were accidentally being institutionalized for wrong reasons
Educational resources could be wasted on children not capable of learning

Binet's Vision:

Education could improve mental abilities, even of "sub-normal" children
Science could accurately test every person for their aptitudes
Society could assign people to tasks with utmost efficiency
These goals required a scientifically accurate intelligence test

Early Mental Testing Attempts

Cattell's Mental Tests (1890)

James McKeen Cattell published "Mental tests and Measurements" in 1890. Like Galton, Cattell was also a proponent of eugenics. Cattell proposed measuring each person on ten tests:

Dynamometer Pressure (hand strength)
Rate of Movement (hand speed)
Sensation-areas (distinguishing pin-pricks)
Pressure causing Pain
Least noticeable difference in Weight
Reaction-time for Sound
Time for naming Colours
Bi-section of a 50 cm line
Judgment of 10 seconds time
Number of Letters remembered on once Hearing

Cattell's tests ranged across physical and mental abilities, but none measured a complicated concept like human intelligence. By 1896, Cattell had collected extensive data on Columbia University students, including:

Physical measurements (hair/eye color, height, weight, head size)
Sensory abilities (vision, hearing, touch)
Cognitive measures (reaction time, memory, mental imagery)
Examiner judgments of student quality
Detailed family and medical history questionnaires

Binet's Critiques of Early Approaches

Binet criticized the early approaches to mental testing, arguing that they failed to measure complex mental processes that constitute intelligence. He advocated for tests that would assess higher-order cognitive functions rather than simple sensory and motor abilities.

The Binet-Simon Test (1905-1911)

Motivation

Binet was commissioned by the French government to develop objective methods for identifying children who needed special educational assistance. The goal was to replace subjective and biased assessment methods with scientific testing.

Method

The Binet-Simon test introduced several revolutionary concepts:

Age-Based Norms:

Tests were designed to measure abilities typical of different age groups
Children's performance was compared to age-appropriate expectations
This allowed for identification of developmental delays or advances

Complex Cognitive Tasks:

Unlike Cattell's simple sensory tests, Binet included complex reasoning tasks
Tests measured comprehension, judgment, reasoning, and problem-solving
Tasks increased in difficulty and complexity

Binet's Mental Testing Procedure

Figure: Examples of questions and results from Binet's mental testing procedure. The figure shows individual tasks that were determined to be appropriate for children in each year, from 3 to 13, along with sample results demonstrating age-related performance differences and individual variations within age groups.

Quantifying Mental Ability with Age

Binet introduced the concept of "mental age" - the chronological age at which a child's performance was typical. This allowed for:

Objective comparison between children
Identification of developmental patterns
Educational planning based on cognitive readiness

Computing Intelligence Scores

The intelligence quotient (IQ) was later developed by German psychologist William Stern:

IQ Formula: IQ = (Mental Age / Chronological Age) × 100

Average intelligence: IQ = 100
Above average: IQ > 100
Below average: IQ < 100

Binet's Use Cases

Binet envisioned several applications for his test:

Educational Assessment: Identifying children needing special instruction
Objective Evaluation: Replacing subjective teacher judgments
Resource Allocation: Efficiently distributing educational resources
Child Welfare: Preventing inappropriate institutionalization

Meaning of the Measure

Binet was cautious about interpreting his test results:

He viewed intelligence as complex and multifaceted
He believed mental abilities could be developed through education
He warned against using tests to label children permanently
He emphasized the test's limitations and need for careful interpretation

Mental Testing and Eugenics in America

The Alpha-Beta Test

During World War I, American psychologists developed group intelligence tests for military use:

Army Alpha Test:

Written test for literate recruits
Included analogies, arithmetic, and general knowledge
Used to classify soldiers for different roles

Army Beta Test:

Non-verbal test for illiterate recruits
Used pictures and symbols instead of words
Attempted to measure "innate" intelligence

Results and Interpretation:

Tests showed differences between ethnic groups
Eugenicists interpreted results as evidence of racial hierarchies
Alternative explanations (education, language, cultural bias) were largely ignored

Scientific Racism

Intelligence tests became tools for promoting racist ideologies:

Misuse of Test Data:

Group differences were attributed to genetic inferiority
Environmental factors were minimized or ignored
Results were used to justify discriminatory policies

Immigration Restrictions:

Test results influenced immigration quotas
Certain ethnic groups were deemed "undesirable"
Scientific veneer was given to racist policies

Mental Health Applications

The eugenics movement deeply impacted mental health policy:

Classification Systems:

"Idiots": mental age of 2-year-olds
"Imbeciles": mental age of 3-7 year-olds
"Morons": mental age of 8-12 year-olds (term invented by Goddard)

Policy Consequences:

Forced sterilization of people deemed "feeble-minded"
Institutionalization based on test scores
Segregation from mainstream society

Henry Goddard's Role:

Director of Vineland Training School
Translated Binet's work into English
Promoted eugenic applications of testing
Advocated for identifying and controlling "morons"

Education and The Black Psychologists

Intelligence testing became widespread in education through standardized testing:

Educational Sorting:

Tests used to track students into different educational paths
Superior children received more resources
"Inferior" children received limited educational opportunities

Achievement Gaps:

Testing revealed differences between ethnic groups
Gaps were often attributed to innate differences rather than systemic inequalities

Formation of ABPsi (1968):
The Association of Black Psychologists was formed to address concerns about testing:

ABPsi's Position on Testing:
The organization opposed tests that were used to:

Label Black children as uneducable
Place Black children in special classes
Provide inferior education
Assign Black children to lower educational tracks
Deny higher educational opportunities
Destroy positive intellectual growth and development

Advocacy and Reform:

Called for moratorium on testing in 1969
Challenged biased testing practices
Promoted culturally fair assessment methods
Achieved moratorium on intelligence testing of Black children in California (1979)

Modern Implications: Testing Abilities vs. Testing Theories

This historical context raises important questions about how scientific research contributes to society:

Lessons Learned

Scientific Responsibility:

Researchers must consider social implications of their work
Tools can be misused even when developed with good intentions
Scientific findings require careful interpretation and application

Ongoing Vigilance:

Testing continues to have positive and negative outcomes for different groups
Cultural bias in assessment remains a concern
Educational and employment decisions based on testing require scrutiny

Contemporary Cognitive Psychology

Modern cognitive psychology has shifted focus:

From Classification to Understanding:

Tests are used to understand how cognition works
Focus on testing theories rather than ranking people
Emphasis on cognitive processes rather than fixed abilities

Methodological Improvements:

Better control for cultural and linguistic factors
Recognition of multiple intelligences
Dynamic assessment approaches
Consideration of contextual influences

Key Takeaways

Historical Context Matters: Intelligence testing developed within the context of eugenics, which shaped its early applications and interpretations.
Scientific Tools Can Be Misused: Even well-intentioned scientific developments can be applied in harmful ways when influenced by social prejudices.
Multiple Perspectives: Binet's educational focus differed significantly from Terman's eugenic applications of the same basic testing principles.
Social Consequences: Intelligence testing had profound impacts on education, immigration, mental health policy, and civil rights.
Ongoing Relevance: The legacy of early intelligence testing continues to influence contemporary debates about assessment, education, and social policy.
Importance of Advocacy: Marginalized communities, particularly Black psychologists, played crucial roles in challenging discriminatory testing practices.
Scientific Evolution: Modern cognitive psychology has learned from this history to focus on understanding mental processes rather than ranking human worth.

Self-assessment & Experiments

This chapter draws from historical sources and contemporary scholarship to provide a comprehensive view of intelligence testing's development and impact. Understanding this history is essential for responsible practice in psychological assessment and cognitive research.

References

Cattell, J. M. (1890). Mental tests and measurements. Mind, 15(59), 373-381.
Binet, A., & Simon, T. (1905). Méthodes nouvelles pour le diagnostic du niveau intellectuel des anormaux. L'Année Psychologique, 11, 191-244.
Terman, L. M. (1916). The measurement of intelligence. Houghton Mifflin.
Goddard, H. H. (1912). The Kallikak family: A study in the heredity of feeble-mindedness. MacMillan.
Yoakum, C. S., & Yerkes, R. M. (1920). Army mental tests. Henry Holt.