The Origins and History of IQ Tests

We’ve all heard of IQ tests. Perhaps you’ve taken an official test or anonymously taken many of the ones shared on social media. But what exactly do they mean? Where do they come from? Are they even accurate or representative of “intelligence”? Join us as we take a very quick tour of IQ tests. The following article is far from an exhaustive exploration of what is actually a very large field in psychology but we hope it gives you an overview of the topic.

So what is IQ?

IQ, or “Intelligence Quotient”, is in effect a numerical score based on the results of a standardized test. It is meant to quantify or measure the participant’s intelligence. It was originally developed by French psychologist Alfred Binet. He wanted to measure the mental ability of children but is now used to test adults of all ages. Modern tests involve a combination of several intelligence scales to provide a general indicator of intelligence.

The actual term IQ was coined in 1912 by German psychologist William Stern. The basic test developed by Binet and his colleague Simon have been built on and expanded over the last few decades. Modern IQ tests are now based on the normal distribution of scoring. Due to this fact the term “intelligence quotient” is, in reality, defunct but still widely accepted. Modern tests, often WAIS (more on that later), are used to calculate IQ. These tests, unlike their precursors, involve a number of problems that must be solved in a set time period, under supervision. They test various areas including short-term memory, verbal knowledge, perceptual speed and spatial visualization.

Most tests provide overall scores and individual subtest scores. This allows for an overall assessment of intelligence and your performance in each of the different areas. IQ tests are based on normal distribution bell curve. For this reason, they are only really designed and valid for certain IQ ranges. If you fall into the extremes of the scale they are highly unreliable. It is also interesting to know that your IQ score will not necessarily remain the same over your lifetime!

Here is a good overview video.

Origins of IQ tests

During the early 1900’s, the French Government wanted to find out which students were most likely to struggle in school. The French Government had just passed laws making school attendance compulsory. It was for this reason that it seemed a good idea to identify which children would need special assistance as early as possible. Binet, with the help of his colleague Theodore Simon, began to work on a question set that would let them assess a person’s ability to solve problems, remember facts and assess their attention span. This set of questions then formed the foundations for allowing them to predict likely success in school.

They quickly came to realize that certain children were able to answer advanced questions that older children could answer and vice versa. From these observations, Binet, suggested the concept of mental age. This was intended to be used a metric to determine the average intelligence per age group. Soon after Binet began to develop the first intelligence test. We call this the Binet-Simon scale today which has become the basis for intelligence tests. Despite developing the test Binet was not convinced that psychometric instruments could be used to measure a single, life-long, inborn level of intelligence.

Binet believed that intelligence was such a broad subject that giving a numerical value was insufficient. He believed that intelligence was influenced by a number of factors. He also believed that these changed over time and would only be comparable to children with similar backgrounds and experiences.

IQ test improvements

Standford University, namely psychologist Lewis Terman, took the Binet-Simon Scale and standardized it for American participants. The adapted test, The Stanford-Binet Intelligence Scale, became the standard intelligence test in the US in 1916. From this test, the term Intelligence Quotient was coined and it consisted of a single number. This number was meant to represent an individual’s performance from the tests results. The score was generated by taking the test maker’s mental age by their physical age and the multiplying the result by 100. So, by way of example, if a child acquired a mental age of 12 from the test, but they were 10 years old, their final IQ score would be 120.

Later, psychologist Charles Spearman would go on to develop the concept of general intelligence. This is meant to provide an assessment of a person’s ability to perform a wide range of cognitive tasks. Modern tests tend to focus on abilities such as mathematical skill, memory, spatial perception and your ability to use language. A person’s ability to solve problems, remember information and see relationships are recognized as being important components of one’s intelligence. Owing to this you will commonly see them in IQ tests.

[Image Source: Pixabay]

Wechsler Intelligence Scales

Building on the tests developed by Stanford and Binet, American psychologist David Wechsler decided to create a new metric test. He was dissatisfied with the limitations of the Stanford-Binet test and developed his own version, The Wechsler Adult Intelligence Scale, in 1955. Weschler believed, as Binet did, that intelligence involved difference mental abilities. He believed that intelligence was “the global capacity of a person to act purposefully, to think rationally, and to deal effectively with his environment.” The adult test was later revised and is known today by the abbreviation, WAIS-IV.

Wechsler went on to develop two other tests for use on children. The Wechsler Intelligence Scale for Children (WISC) and the Wechsler Preschool and Primary Scale of Intelligence (WPPSI). The current adult version provides 10 subtests along with 5 supplementary tests. These provide scores in four major areas of intelligence:-
-Verbal Comprehension,
-Perceptual Reasoning,
-Working Memory and;
-Processing Speed.

This test provides two broad scores that can be used to summarize overall intelligence. The first is a full-scale IQ score which combines the performance of all four indices. The second is a General Ability Index based on six subtest scores. The later has been found to be very useful in identifying learning disabilities. Cases, where low scores in some areas may be associated with high scores in other areas, can help identify that the individual was a specific type of learning difficulty.
Unlike the “simpler” Stanford-Binet tests, the WAIS compares scores from other individuals in the same age group. It effectively benchmarks the individual within an age group. The average score is fixed at 100. Two-thirds of scores usually lie within the range between 85 and 115. This method has become the standard technique around the world and is also used in the modern Stanford-Binet test.

So what score makes you a genius?

You may already be familiar with IQ score ranges but what score makes you a genius? Very high IQ’s tend to fall above 140 but to be classified as a genius you need to breach 160 +. There is even an “unmeasurable Genius” level if you record a score exceeding 200! As previously mentioned the average IQ is set to 100. Around sixty-eight percent of IQ scores fall within one standard deviation of this average. So most people will be between 85 and 115.

You are probably familiar with bell curves and IQ is no different. The higher or lower down the scale you move from the “bell peak” average the smaller and smaller the number of individuals who will fall into it. Excessively low 1-24 or excessively high 180+ IQ’s will represent a very very small percentage of the population. As you’d expect the standard deviation will change depending on the number of individuals tested within a group. In IQ testing this tends to be around 15 points plus or minus.
IQ scores are meant to help measure a person’s problem-solving abilities. Could IQ be related to you physical brain structure? Let’s look at Einstein’s brain for example.

So what do Mensa say?

According to Mensa, there can be a discrepancy between tests and your attained score.
“The term “IQ score” is widely used but poorly defined. There are a large number of tests with different scales. The result on one test of 132 can be the same as a score 148 on another test. Some intelligence tests don’t use IQ scores at all. Mensa has set a percentile as a cutoff to avoid this confusion.” Mensa.org
Mensa will only allow entry if you fall within the top two percent percentile of the general population. This score must be provided by Mensa directly or via an “approved” third party test. This is interesting but only provides an arbitrary “cut-off” for high IQ. If you want to have a go at a dry run “for fun” non-qualifying IQ test from Mensa, follow this link.

The importance of IQ to “success”

All well and good, but what do these scores actually mean? How much difference do a few IQ points actually make to an individual’s success in life? There is no doubt that high IQ’s can be strongly linked to academic success. Whilst high IQ is becoming a popular means of assessing a person’s intellect other experts believe that emotional intelligence might matter more than IQ. For success at least.

Most of us have come to believe that high IQ will guarantee success in life, but is this true? It seems that most successful people in science, art, business and entertainment seem to be extremely bright. Interestingly there also exists a stereotype that those with higher IQ’s tend to be socially awkward, introverted or perhaps even mentally unstable. This is usually crystallized in popular cultures such as characters like Sheldon Copper in The Big Bang Theory or the somewhat unstable Sherlock Holmes.
You may well know, or indeed be, an extremely intelligent people who are very successful but you can probably think of others who are not quite as successful as you might have expected. So why the disparity? Since the early days of IQ testing from Binet et al, this very question has been asked many times before. Psychologist Lewis Terman, as early as the 1920’s, began to investigate this question. The premise was that genius-level IQ’s tended to be associated with social and personal “maladjustment”. He selected 1500 children between the ages of 8 and 12 with IQ’s of at least 140. The average for the group was 150 with 80 of them exceeding IQs of 170!

So just how “successful” were the group?

Over the following years, he tracked the children’s lives to see how they performed “in the real world”. Seemingly contrary to expectations, these children tended to be very well socially and physically well adjusted. They were academically successful, tended to be healthier, stronger and even less accident prone compared to children of lower IQ. Terman passed away in 1956 but his research was continued by other psychologists on the very same group. The study came to be known as the Terman Study of the Gifted.
This study even continues to this day! This makes it the longest running longitudinal study in history! Some of the study group went on to achieve great success in life. The group included the famed educational psychologist Lee Cronbach, author Jess Oppenheimer, child psychologist Robert Sears, scientist Ancel Keys and many more who became faculty members at colleges and Universities. As of 2003, 200 of the original participants were still alive and the study is set to continue until the members die or withdraw.
When the group was checked up on in 1955 the average yearly income was around $5,000. Unbelievably, the average income for the group was on the order of around $33,000! Of the group members, sixty-six percent had earned college degrees with a large amount earned graduate and professional degrees. Lots of the group pursued careers in law, medicine, and science with others becoming successful business executives!

Were they all “successful”?

The story wasn’t “all roses” however. Researcher Melita Oden decided to compare the most successful 100 individuals, Group A , with the 100 least successful, Group C. These individuals effectively had the same IQ but only a few of from Group C had become professionals. Although most of the members of Group C earned slightly above the national average they showed high rates of alcoholism and divorce rates compared to Group A.
Considering there was no noticeable distinction in IQ between the two groups what could possibly explain the difference in behavior and “success”? Terman himself noted that the top 100 individuals from his study group showed some very interesting common traits. They exhibited “prudence and forethought, willpower, perseverance, and the desire to excel.” As adults, these individuals tended to rate higher on goal-orientation, self-confidence, and perseverance compared to group C.
Whilst the observations above are somewhat subjective, IQ does seem to play a role in life success, but is not a guarantee for “success”. Personality traits are also very important.

Modern studies on IQ and success

IQ certainly can be used to predict an individual’s likelihood of academic success. It can’t be used to satisfactorily predict their performance outside of academia, however. Professor Alan Kazdin, Professor of Psychology at Yale University notes that “The best thing IQ measures is the ability to do well in school”.  He goes on to say that “At this age, consider it potential. But you have to have the right environment to nurture this.”

Makes sense. It has become well known that we are all a product of “nature and nurture”. Other research indicates that children with exceptional academic abilities may experience more social problems, including isolation compared to less “gifted” children. One study even found that high IQ tend to score high on a personality trait known as “openness to experience”. Whilst this sounds somewhat benign it can actually translate to the individual to try narcotics such as marijuana. Since they are more willing to try new things they are more likely to seek “novel” experiences.
Despite many contemporary researchers debating the extent to which IQ influences life success, most broadly support Terman’s findings.

How accurate are they?

As with any formalized test, the results from it are only as good as the test itself. Controversy aside and given that there is a formalized test, it is a good a valid question to ask. As previously mentioned, modern IQ tests are only reliable if your fall within the IQ scale. If your IQ test score provides scores at the extremely low or high it cannot accurately reflect your score. According to the test criteria of course.

So are IQ tests valid or accurate? Depending on your point of view about their validity on the first place, IQ tests scores are a generally accepted metric for benchmarking an individual’s intelligence, at least for academic performance. The following video is narrated by Laci Green (yeah sorry) but provides an interesting discussion nonetheless (for a change).

What affects IQ?

There is much controversy over what affects IQ test scores in individuals. Studies have shown that your IQ seems to be affected by environmental factors such as childhood nutrition, prenatal exposure to toxins and duration of breastfeeding. Some other studies seem to show a correlation with parental social status, parental IQ amongst other factors. This is an area of intense debate and controversy and it is unclear how much IQ is inheritable and vice versa. It should be noted that others believe that IQ is a redundant term as intelligence cannot be measured as a single entity. IQ may not even be genetically determined! Some have even proposed that each individual possesses multiple intelligence’s and development of each depends on your social background.

Think of a computer game where you can customize your character. You’re born or created with potential with different “abilities” that are only developed based on your upbringing and social circle. Jim Rohn, a famous motivational speaker is famous for saying that everyone is the “average of the five people you spend most of your time with”, for example.

Whatever the truth is IQ test scores are still widely used in many contexts in modern society. But can it change? Is it fixed from birth or can it be improved over your lifetime?

Can your IQ change over your lifetime?

According to Stephen Ceci, Professor of Developmental Psychology at Cornell University, they can. In an article written in Nature, IQs seem to be able to change over time. They took 33 adolescents, between 12 and 16 years old. The researchers gave the students tests prior to starting their studies. They then retested them four years later. Test results noted a marked fluctuation in IQ tests. The results weren’t a negligible change but rather a change of 20 or so points. The main changes primarily seemed to be an improvement in verbal ability. Other studies show that IQ can change depending on other factors too. Many seem to show a correlation between “life” experiences, such as schooling or structured learning. Activities that develop learning patterns or grouping things systematically, rather than thematically, seem to improve your performance on IQ tests.

Yet other studies seem to show that taxi drivers’ or even young adults’ learning skills like learning routes or juggling improve their navigational skills and pattern identifying abilities. Put together the results of these studies show that life experiences and structured learning change the brain and IQ. This is true of adults as well as children! This shouldn’t really come as a surprise. The more you become experienced with seeing patterns or identifying “trick questions” say, the more likely you will pay attention and think logically to work out the answer. This is especially true if your work or hobbies relate to tasks like puzzles, coding or mathematics e.g. Soduku.

The final word

IQ tests have historically been used to assess a person’s intelligence but have come under a lot of “fire” in recent years. Whether you feel they are an accurate measure of intelligence or an obsolete metric, the tests certainly do seem to show a “potential” for success in academia, but not necessarily success in life.

IQ tests have been misused in the past to justify some pretty horrific ideological programs and can be an emotive subject, but they need to be thought of as they were originally intended. As a metric, a measurement of something that can be tested, nothing more. At the end of the day, you can measure anything on any scale. But the results you get are only as useful as the test itself. How you use that information or how you react emotionally to it are, in the end, irrelevant to the results of an arbitrary test.


So there you go. We have explored the origins of IQ tests and briefly touched on what they entail. Do you believe IQ tests are an accurate representation of intelligence? Are they just an arbitrary metric that is now obsolete? Let’s start a conversation.