IQ, or intelligence quotient, is simply a measure of a person’s cognitive abilities, providing a score that reflects intellectual potential and reasoning skills. IQ tests and IQ testing have quite a long history, dating back over 100 years. The earliest well-known intelligence test was developed by French psychologist Alfred Binet in the early 1900s. However, the concept of measuring intelligence began to take shape even earlier with the work of psychologists like Sir Francis Galton, who believed that intelligence could be quantified and studied scientifically. These days, IQ has become a widely recognized tool for assessing intelligence and cognitive abilities.
Known as the Binet-Simon Scale, the first recognized IQ test was released in 1905 and focused on abilities like memory, attention, and problem-solving. Still, the journey of IQ testing history began with Sir Francis Galton, one of modern-day intelligence research’s fathers, who had a strong influence on Alfred Biner and his works.
Galton, in the late 19th century (1800s), laid the groundwork for future developments with his attempt at developing a standardized test for assessing the intelligence of a person. Though Galton’s methods lacked accuracy by today’s standards, his ideas and testable hypotheses about intelligence inspired later psychologists, including Alfred Binet, who created the first recognized IQ test.
In the early 1900s, Binet was tasked by the French government with developing a tool to identify students who needed extra educational support. Binet, working alongside his colleague Théodore Simon, created the Binet-Simon Scale—the first standardized test resembling a modern intelligence test, with a series of questions aimed at measuring cognitive ability. The test was then revised in 1908 and 1911, with the 1908 version being the first to include scaling to assess mental age.
The Binet-Simon Intelligence Scale quickly became the basis and groundwork for the development of IQ tests that are still in use these days. However, it has its own limitations, such as offering an incomplete measure of intelligence or not comprehensively accounting for the complexity of many factors that can influence intelligence. Later psychologists made modifications needed to create more comprehensive tests that better account for the multifaceted nature of intelligence.
French psychologist Alfred Binet
In 1916, Lewis Terman, an American psychologist at Stanford University, revised and adapted Binet's test for use in the U.S.
Terman's version, known as the Stanford-Binet Intelligence Scale, introduced the IQ score, which is calculated by dividing the mental age by the chronological age of an individual and multiplying by 100. To illustrate, a child with a mental age and chronological age of 10 and 12, respectively, would have an IQ score of 120 (20: (12÷10) x 100 = 120).
These days, this scale is still a popular assessment tool, in spite of going through various revisions over a century since its inception.
During World War I (1914–1918), the need for efficient assessment of military recruits led to the development of the Army Alpha and Beta tests. In 1917, psychologist Robert Yerkes and his team designed these two IQ tests, which were administered to more than 2 million soldiers.
The Army Alpha test was a written exam for literate recruits; the Army Beta test, on the other hand, was a non-verbal assessment for non-English-speaking and illiterate recruits. These tests aimed to quickly evaluate the cognitive abilities of soldiers and place them in appropriate roles.
The success of these tests demonstrated the practicality of IQ testing on a large scale and influenced the development of future assessments. Notably, even after the war, these tests were still used in various situations outside of the military.
Another American psychologist who significantly contributed to the evolution of IQ testing is David Wechsler. In 1955, he introduced the Wechsler Intelligence Scales (WAIS) to address the limitations he saw in existing intelligence tests, particularly the Stanford-Binet.
Wechsler first created two different test versions for use with children: WPPSI (the Wechsler Preschool and Primary Scale of Intelligence) and WISC (the Wechsler Intelligence Scale for Children). He also developed WAIS (the Wechsler Adult Intelligence Scale)—the test’s adult version.
Interestingly, the WAIS is not scored based on mental and chronological age. Instead, it’s scored by comparing the score of the test taker to that of others in the peer group. 100 is fixedly set as the average score, with approximately 68% (around ⅔) of scores falling within the normal range, somewhere between 85-115 (looking at the bell curve of the IQ score distribution can help you clearly understand this).
This scoring method has been considered the gold standard in IQ testing, and the Wechsler Scales have also become one of the most widely used intelligence tests globally, valued for their comprehensive structure and adaptability in measuring cognitive strengths.
Over the years, the Wechsler scales have undergone several revisions, maintaining their status as some of the most widely used and respected tools in psychological assessment.
In the 21st century, traditional views of intelligence are evolving, with new approaches to more comprehensively assess the potential and capabilities of a person.
IQ tests are still used but are often viewed as only one component of understanding intelligence. There is an increasingly growing recognition of the role of emotional intelligence (EI), creativity, and other non-cognitive factors in personal & professional success.
Meanwhile, Howard Gardner’s multiple intelligences theory, which includes linguistic, logical-mathematical, and interpersonal intelligences, etc., has expanded the understanding of intelligence beyond cognitive abilities.
These modern perspectives highlight the importance of recognizing intelligence as a multifaceted concept that fuels creativity, collaboration, and personal growth.
Additionally, today’s digital era has seen a bloom of unofficial online IQ tests, making IQ testing more accessible than ever. These tests offer a quick, convenient, and entertaining way for individuals to explore their cognitive abilities.
Despite their widespread use globally, IQ testing and IQ tests are not without controversy. Debate over whether the IQ test is a robust and reliable measure and what it really means to be “intelligent” has continued over the years.
One of the major concerns is cultural bias; some researchers argue that the 'cultural specificity' of intelligence may result in IQ tests being biased towards the contexts and environments in which they were created. So, using the same test across different communities would overlook the distinct cultural values that define what each community considers to be intelligent behavior. That may, of course, lead to inaccuracies in measurements.
Additionally, whether or not the test results are influenced by outside factors like coaching, quality of schooling, health status, motivational level, and so on is also another big concern. Critics also argue that the tests do not account for the many factors impacting a person’s full intellectual capacities, such as emotional intelligence, creativity, and social skills.
To conclude, the history of IQ test is a fascinating and complex journey, from early hypotheses to modern applications, with significant changes in the measurement of intelligence through the years. From Binet's pioneering work to modern assessments, IQ tests have evolved to become a crucial tool in understanding human intelligence, though they've been facing criticism and controversy. These days, the test is applied in various areas and for multiple purposes, such as educational assessment, job candidate evaluation, cognitive research, assessing cognitive abilities, and more.
