What does it mean to be smart? For over a century, one deceptively simple number has attempted to answer that question. The intelligence quotient — IQ — has been used to screen soldiers, educate children, and crown geniuses. It has shaped careers, influenced policy, and sparked fierce debate. Yet the more scientists study the human mind, the clearer it becomes that intelligence is far too vast and strange a thing to be captured in a single score.

Albert Einstein—perhaps the most celebrated intellect of the modern era— had an estimated IQ of around 160. That is extraordinary by any measure. And yet, there are individuals who have scored well above him: William James Sidis, a child prodigy of the early twentieth century, is estimated to have had an IQ somewhere between 250 and 300. Marilyn vos Savant holds a recorded IQ of 228. These numbers raise an uncomfortable question: does the highest IQ truly make someone the smartest person in the world?

The birth of the test

The story begins in the late nineteenth century with Sir Francis Galton, an English polymath and the founder of differential psychology. Galton believed that intelligence was hereditary and could be measured through sensorimotor tasks — the speed and accuracy with which the brain receives a signal and produces a response. His ideas were rigorous for their time, though they carried troubling assumptions about heredity and race that would haunt the field for decades.

Around the turn of the century, a French lawyer-turned-psychologist named Alfred Binet took a more practical approach. In 1904, the French government commissioned him to identify which children were likely to struggle most in school. Working with his colleague Théodore Simon, Binet devised a series of thirty questions targeting attention, memory, and problem-solving — skills that shape learning, not merely recall. The result was the Binet-Simon Scale: the world's first official IQ test.

It has always seemed odd that we like to call the human brain the most complex object in the Universe, yet many of us still accept that we can measure brain function with a few IQ tests.

Roger Highfield, Director of External Affairs, Science Museum London

A century of evolution

1916

Stanford-Binet Scale

Lewis Terman of Stanford University translates and standardizes Binet's test, introducing a two-scale measurement system for greater accuracy.

1917

Army Alpha & Beta tests

Psychologist Robert Yerkes develops written and picture-based IQ tests to assess U.S. Army recruits — and, controversially, to screen immigrants at the border.

1955

Wechsler Adult Intelligence Scale

David Wechsler creates the modern gold standard, comparing scores within age groups. The revised WAIS-IV fixes the average at 100, with two-thirds of people scoring between 85 and 115.

2012

The landmark study

A study of 46,000 people across the globe finds that no single measure of intelligence — including IQ — can capture the three distinct components of human cognition: short-term memory, verbal ability, and reasoning.

A dark chapter

IQ testing has not always been used in service of human flourishing. In the early twentieth century, tests were used to screen immigrants entering the United States, with government officials citing supposedly "inferior" scores to justify discriminatory restrictions on entire ethnic groups. This history is a reminder that a tool designed to understand the mind can be turned into a weapon of exclusion when divorced from ethical scrutiny.

The limits of a number

The case of Christopher Langan — sometimes called "the smartest man in America," with a reported IQ between 195 and 210 — illustrates the problem vividly. Despite his extraordinary scores, Langan has publicly promoted September 11th conspiracy theories and white replacement ideology, leading some commentators to describe him, memorably, as "Alex Jones with a thesaurus."

A high IQ, it seems, is no guarantee of wisdom, judgment, or intellectual humility. Critics have long called IQ tests "fundamentally flawed," arguing that they measure not raw intelligence but a combination of motivation, quality of schooling, health status, and cultural familiarity with the test format itself.

The 2012 study referenced above found that intelligence is not a single river but a delta—branches into at least three distinct streams. No single score can map all of them. Some researchers wrote:

"We have shown that the idea of a general intelligence expressed as a single number is just wrong,"

Why it still matters

None of this means IQ is useless. At a population level, IQ scores correlate meaningfully with academic achievement, certain job performance outcomes, and even health indicators. Used carefully and in combination with other measures, they remain a valuable tool for researchers and educators. The problem arises when IQ is treated as a verdict rather than a variable — when a number is used to declare someone smart or not smart, capable or incapable, worthy or unworthy.

The truest measure of a mind may be something IQ tests were never designed to capture: curiosity, resilience, creativity, empathy — the capacity to keep learning in the face of what you do not yet know. Einstein understood this.

The measure of intelligence," he reportedly said, "is the ability to change.

Sources: Verywell Mind; The Independent (2012 cognitive study); AllThatsInteresting.com, "27 Geniuses With The Highest IQs In History" (March 2026).