In the early 1900s, the French government asked Alfred Binet to develop a test of intelligence for children. What was the original purpose of that test?
Choose an answer, then check it.
Psychology · Foundations
Intelligence
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In 30 seconds
intelligence The ability to learn, reason, and solve problems — the working definition used in this lesson; psychologists continue to debate the exact definition. Full entry → is the ability to learn, reason, and solve problems — the working definition used here, drawn from the APA Dictionary of Psychology and the Noba Project. Experts still debate exactly what intelligence is, and an IQ score, from an intelligence test A standardized test that measures abilities such as solving problems, forming concepts, and reasoning. Full entry →, captures only part of the picture. Psychologists have proposed one general ability (Spearman's g), many separate abilities (Gardner's multiple intelligences Howard Gardner's theory that each person possesses several relatively independent kinds of intelligence, such as linguistic and spatial, rather than one general ability. Full entry →), and three interacting kinds (Sternberg's triarchic theory). Genes and environment both shape it. No number captures a person.
Why this matters
Almost everyone has met an IQ score — their own, a friend's, or one quoted in a headline. Understanding what that number does and does not mean changes how you read it: in schools, where tests help decide who gets support; in hiring and placement, where scores influence decisions; and in everyday talk, where people quietly rank themselves and others. The measurement debate matters academically because it sits at the center of psychology's oldest questions — what the mind is and how to study it. Practically, it keeps a useful tool in its place: a sample of some abilities, not a verdict on a person. And honestly, it is a reminder that the most important measures of a person rarely come with a scale.
The college version
What intelligence is
Intelligence is the ability to learn, reason, and solve problems. That working definition compresses the ones psychologists actually use. The APA Dictionary of Psychology defines intelligence as the ability to derive information, learn from experience, adapt to the environment, understand, and correctly utilize thought and reason. The Noba Project's intelligence module, by psychologist Robert Biswas-Diener, describes intellectual ability as encompassing the ability to learn, remember, and use new information, to solve problems, and to adapt to novel situations. Compress both and you get the working definition of this lesson: learn, reason, solve. The honest note comes immediately: experts do not agree on a single definition. OpenStax Psychology 2e puts it directly — what exactly is intelligence? The way researchers have defined the concept has been modified many times since the birth of psychology. Some argue for one broad ability; others argue for many separate ones. That debate is part of the topic, not a gap in it.
The IQ idea: a score with a history
IQ stands for intelligence quotient, and it describes a score earned on a test designed to measure intelligence. The APA Dictionary defines IQ as a standard measure of an individual's intelligence level based on psychological tests; the average is customarily set at 100, and most scores fall within fifteen points of it. The score has a specific origin story. In the early 1900s, the French government asked Alfred Binet to develop an intelligence test to use on children — not to rank them, but to determine which ones might have difficulty in school, so they could get help. American researchers saw the value of the idea: Lewis Terman, a Stanford professor, standardized Binet's work into the Stanford-Binet Intelligence Scale, still used today. In 1939, David Wechsler built his own test from subtests covering verbal and nonverbal skills, because he believed intelligence was a global capacity to act purposefully, think rationally, and deal effectively with the environment. Modern IQ tests descend from those tools.
Three theories of intelligence
Over the last century, psychologists have proposed very different answers to what intelligence is. Charles Spearman, a British psychologist, argued that intelligence consists of one general factor, called g, which could be measured and compared among individuals — the observation behind it being that people who perform well in one intellectual area tend to perform well in others. The APA Dictionary credits the idea of the general factor (g) to Spearman in 1904. Howard Gardner, a Harvard psychologist, took the opposite direction: his theory of multiple intelligences holds that each person possesses at least eight relatively independent intelligences — linguistic, logical-mathematical, musical, bodily-kinesthetic, spatial, interpersonal, intrapersonal, and naturalistic. Gardner's theory is widely used in education, though OpenStax notes it has been heavily criticized among cognitive psychologists for lacking empirical evidence. Robert Sternberg's triarchic theory of intelligence Robert Sternberg's theory that intelligence has three parts — analytical, creative, and practical. Full entry → offers three parts: analytical intelligence, close to academic problem solving — analyzing, evaluating, judging, comparing; creative intelligence, inventing or imagining novel solutions; and practical intelligence, sometimes called street smarts — finding solutions that work in everyday life by applying knowledge from experience.
Tests today: some abilities, not the whole person
Modern IQ tests measure real abilities. The APA Dictionary describes the intelligence test as an individually administered test measuring the ability to solve problems, form concepts, reason, acquire detail, and perform other intellectual tasks. But those abilities are a sample, not the whole person — and the people who built the tests said so. Wechsler was suspicious of using a single score to capture all of intelligence, and he designed his test to tap a variety of verbal and nonverbal skills. OpenStax reports that IQ tests have been debated throughout their development and use: they have sometimes been used for harmful purposes, such as supporting the eugenics movement, and the question of how valid they are remains open. Scores even drift across generations: the Flynn effect is the observation that each generation scores higher than the last, which Flynn argued does not necessarily mean greater intelligence. A score is a measurement of some abilities at one moment, not a biography.
What shapes intelligence: genes and environment
Genes and environment both matter. The classic evidence comes from twin studies. In the Minnesota Study of Twins Reared Apart, researchers found that identical twins raised together and identical twins raised apart show higher correlations between their IQ scores than siblings or fraternal twins raised together — a finding OpenStax reports as revealing a genetic component to intelligence. At the same time, other psychologists emphasize the developmental environment; OpenStax's summary of the field is direct: aspects of each idea are probably correct. The range-of-reaction idea captures the balance: a person's genetic potential is a fixed quantity, but whether that potential is reached depends on the environmental stimulation experienced, especially in childhood. No single gene, classroom, or number explains a person's intelligence.
The honest framing: a verb, not a noun
The reality check that holds the lesson together: a number does not capture a person. A score is a measurement taken at one time, from one set of tasks, under one set of conditions; the person is a learner who changes, practices, and adapts. That is why the honest framing of this lesson is that intelligence is a verb, not a noun — it is something people do, learning, reasoning, solving, more than something they have. Treating it as a fixed noun, a rank carried for life, is where the measurement debate does its damage. Treating it as activity keeps both the science and the humility: measure what can be measured, and remember what the measurement leaves out.
Eli explains
The same idea, in plain words
Explain it like I’m 10
Intelligence is the name psychologists give to the ability to learn, reason, and solve problems. No one owns a perfect definition — the experts debate it, and that debate is part of the story. The number you have probably heard of is IQ, the score from an intelligence test, and it measures real abilities: solving puzzles, reasoning, remembering facts. But it is a sample, not the whole person. Over a century, three famous theories have emerged. Spearman said intelligence is one general thing, g, that shows up across everything you do. Gardner said no — people have at least eight different intelligences, from musical to spatial to interpersonal. Sternberg said it is three: analytical, creative, and practical. What makes it grow? Genes and environment, together — twin studies show a genetic hand, and experience shows the environment's. The honest bottom line: intelligence is a verb, not a noun — something you do, more than a rank you carry. No number captures a person.
Picture it like this
Think of a kitchen and a chef. The pantry holds the ingredients — that is the genetic starting material. The chef's training, the recipes tried, and the kitchen she practices in are the environment. The dish she produces on a given night depends on the task in front of her. Now imagine rating the chef's entire ability by a single number from one taste test of one dish. The number says something real about that dish on that night — and almost nothing about the hundreds of dishes she could still learn to cook.
Where the picture stops working
The analogy breaks down because a chef can be retrained and a kitchen restocked, while a person cannot swap genes, and intelligence is not only visible in performances. It also risks sounding like scores are worthless — they are not. A well-built test does measure real abilities. The point is that a measurement is a sample, not the whole.
Worked example
Dev, a sophomore, took an IQ-style test for a research study and scored near the middle of the distribution. The research assistant handed him the number with a caution: it samples some abilities, it does not describe a person. That same semester, the irrigation system in his family's greenhouse kept failing. Dev spent three weekends diagnosing it — forming a hypothesis about a blocked valve, testing it, learning from the failure, trying again — until he found the real culprit, a corroded sensor. No test he had ever taken asked about corroded sensors, and none had measured his patience for failure. A year later he retook the study's test and scored higher, with no coaching in between. Neither score was a lie. Each was a real sample of some abilities at one moment. The number was part of the story; Dev was the rest.
Key takeaway
Intelligence is the ability to learn, reason, and solve problems — an activity, not a fixed rank. IQ scores measure some abilities, not the whole person, and genes and environment both shape the person behind the number.
Quick check
3 questions here, of 5 in this lesson’s practice set. Answers stay hidden until you check.
A student reads that a classmate scored an IQ of 115 on a modern intelligence test. Which description of what that number means is most accurate, according to the APA Dictionary of Psychology?
Choose an answer, then check it.
Rosa's car battery dies in a cold parking lot. Instead of calling for help, she wraps the battery in a warm blanket, waits, and the car starts — a fix she learned from years of maintaining farm equipment, not from a manual. In Sternberg's triarchic theory, which kind of intelligence is Rosa showing?
Choose an answer, then check it.
Study tools & related lessonsYou’ll learn to · Common mistakes · Easily confused · Key vocabulary · Related
You’ll learn to
- Define intelligence using the working definition — the ability to learn, reason, and solve problems — and explain why experts continue to debate the definition.
- Explain what an IQ score is and describe the original purpose of Alfred Binet's intelligence test.
- Distinguish Spearman's theory of general intelligence (g), Gardner's theory of multiple intelligences, and Sternberg's triarchic theory, with attribution to each theorist.
- Explain what modern intelligence tests measure and what they leave out.
- Analyze the evidence that genes and environment both shape intelligence.
- Evaluate the claim that no single test score captures a person.
Common mistakes
"An IQ score measures your total intelligence, once and for all."
A score reflects some measured abilities on one test at one time. Psychologists note that the validity of intelligence tests is still debated, scores shift across generations (the Flynn effect), and no single number captures a person.
"Binet invented IQ testing to rank people by ability."
Binet's test, requested by the French government, was meant to identify children who might have difficulty in school so they could get help — a purpose of finding who needs support, not a lifetime ranking.
"Gardner's multiple intelligences is the settled scientific theory of intelligence."
Gardner's theory is influential and widely used in education, but cognitive psychologists have heavily criticized it for lacking empirical evidence; it is one theory among several, not a settled answer.
"Intelligence is fixed by genes, or else purely made by the environment."
Research supports both: twin studies show a genetic component, and the range-of-reaction view holds that reaching your potential depends on environmental stimulation, especially in childhood.
Easily confused
Spearman's general intelligence (g) vs. Gardner's multiple intelligences
Spearman proposed a single general factor that underlies performance across many kinds of intellectual tasks; Gardner proposed at least eight relatively independent intelligences. The one-ability versus many-abilities question is the heart of the measurement debate.
Analytical intelligence vs. practical intelligence
In Sternberg's triarchic theory, analytical intelligence is close to academic problem solving — analyzing, evaluating, comparing — while practical intelligence means finding solutions that work in everyday life by applying knowledge from experience, sometimes called street smarts.
Intelligence vs. an IQ score
Intelligence is the ability to learn, reason, and solve problems; an IQ score is a measurement of some of those abilities taken from one test at one time. The score is a sample of part of the ability; intelligence is the whole activity.
Key vocabulary
- intelligence
- The ability to learn, reason, and solve problems — the working definition used in this lesson; psychologists continue to debate the exact definition.
- IQ (intelligence quotient)
- A standard score earned on a test designed to measure intelligence; the average score is customarily set at 100.
- general intelligence (g)
- The single general factor proposed by Charles Spearman that is believed to underlie performance across many kinds of intellectual tasks.
- multiple intelligences
- Howard Gardner's theory that each person possesses several relatively independent kinds of intelligence, such as linguistic and spatial, rather than one general ability.
- triarchic theory of intelligence
- Robert Sternberg's theory that intelligence has three parts — analytical, creative, and practical.
- intelligence test
- A standardized test that measures abilities such as solving problems, forming concepts, and reasoning.
- heritability
- A statistical estimate of how much of the variation in a trait within a population comes from genetic differences.
Sources & references
- Psychology 2e, 7.4 What Are Intelligence and Creativity? — OpenStax, Rice University
- Psychology 2e, 7.5 Measures of Intelligence — OpenStax, Rice University
- Psychology 2e, 7.6 The Source of Intelligence — OpenStax, Rice University
- Intelligence — APA Dictionary of Psychology — American Psychological Association
- IQ — APA Dictionary of Psychology — American Psychological Association
- Intelligence test — APA Dictionary of Psychology — American Psychological Association
- General factor — APA Dictionary of Psychology — American Psychological Association
- Triarchic theory of intelligence — APA Dictionary of Psychology — American Psychological Association
- Heritability — APA Dictionary of Psychology — American Psychological Association
- Intelligence — Noba Project — Noba Project (Diener Education Fund)
EliExplains lessons are original prose written from the open, credible references above. See Copyright & Licensing.
Researched 2026-08-22
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