Ever wonder what it actually means to be “smart,” or how an IQ score is truly calculated? In this video, we pull back the curtain on the psychology of human intelligence, breaking down what it is, what it isn’t, and how clinical professionals actually measure it.
From the difference between fluid vs. crystallized intelligence to the formula behind your IQ, we look past the unreliable online quizzes to explore real, standardized cognitive testing.
To begin, let’s start with the question, what is intelligence? Right from the get-go, this is where things can get tricky. It’s not uncommon for people to think of intelligence as one thing, but that’s not accurate. Instead, it is a mix of many different skills and abilities. If we try to define intelligence broadly, the American Psychological Association gives the definition of “the ability to derive information, learn from experience, adapt to the environment, understand, and correctly utilize thought and reason”.
There are other ways we can think about intelligence though. You might also run into the term “fluid intelligence”. This is a general ability to think through and figure out something new that one hasn’t encountered before. There is also the term “crystallized intelligence”. This is using information and knowledge that one already has to solve a problem.
Often, when we talk about intelligence, we’re referring to the combination of multiple skills, areas of information, and overall problem-solving abilities. If we are talking about a specific area of information or skill, we are then referring to an aptitude. In other words, someone can have a strong skill set with one thing, such as art—or even more specifically, painting—and we would then say that this person has an aptitude for art since they have an ability to learn or have learned about art or painting.
Chances are, when a person talks about intelligence, they will reference IQ. Nowadays, this is a term that is used generally to reference the level of one’s intelligence. However, it is actually a technical term that is the outcome of some intelligence assessments. IQ stands for Intelligence Quotient and was coined by William Louis Stern. He came up with the formula for determining IQ, and this remains today in select intelligence tests. Also called a “ratio IQ”, IQ is determined by taking the mental age of someone based on their assessment, dividing this by their chronological age, and multiplying that by 100. When it comes to IQ, someone with a perfectly average intelligence would have an IQ of 100. Scores above 100 are showing a higher IQ, and scores below 100 are showing a lower IQ.
Let’s quickly review a few people who have been important for our understanding of intelligence.
Francis Galton
First up is Sir Francis Galton. He felt that intelligence was a single thing, which is something that is not supported now. Although Galton’s views have not continued to be supported, he was a major pioneer of the thought that people have individual differences in their intelligence and cognitive functioning. He also thought that there may be a genetic component to intelligence, meaning that a level of intelligence would run in families. That said, Galton was known for his work with eugenics and actually invented the term.
J. P. Guildford
Second, let’s go over the view of J. P. Guildford. He was an American psychologist, and his work found 120 factors that can contribute to intelligence. He also came up with terms like “divergent thinking” which is the “ability to generate a novel idea”, so this might be somewhat similar to fluid intelligence. And he also brought about the term “convergent thinking” which is a person bringing multiple thoughts or ideas together into a single, more unified idea.
Alfred Binet & Theodore Simon
Finally, we have Alfred Binet and Theodore Simon. Binet was a French psychologist and Simon was a French psychiatrist. These two were the first to create a standardized test for intelligence, called the Binet-Simon Intelligence Test. They did so to test for intellectual disabilities in children in Paris, France. Their test would go on to later become the Stanford-Binet test, which we’ll discuss shortly.
With tests for intelligence, it’s important that we remember the concepts of validity and reliability. If you want to brush up on those concepts, check out my video on them. This includes What are Validity & Reliability?, What is Reliability? and Types of Validity. Without going down an entire rabbit hole here, you can definitely find intelligence tests online. But, chances are they aren’t going to have the reliability and validity that we’d hope for. So, it’s probably best to skip those and seek out testing that is going to have more consistent results. That’s where the following assessments come into play.
When it comes to tests for intelligence, they are going to have different pros, cons, and other factors that we want to be mindful of. For one, these assessments are going to vary by the age of the person taking the test. Second, different assessments measure different areas of knowledge. For example, the Stanford-Binet measures the mental abilities called fluid reasoning, quantitative reasoning, visual-spatial processing, and working memory.
If you’re not familiar with these, fluid reasoning is basically fluid intelligence. In this case, knowledge is roughly looking at crystallized intelligence. Quantitative reasoning is measuring a person’s ability to solve problems involving numbers. Visual-spatial processing is working with and measuring a person’s ability to manipulate shapes, puzzles, and the space involved to figure these out. And then working memory we can think about as short-term memory.
The Stanford-Binet’s assessment areas differ from the Wechsler tests, which measure verbal comprehension, perceptual reasoning, working memory, and processing speed. On these assessments, verbal comprehension tests a person’s vocabulary, their ability to find similarities in things, and general information that they have. Their perceptual reasoning is measured similarly to visual-spatial processing, where they have puzzles and shapes and need to manipulate these. Working memory is again a test of short-term memory. And finally, their processing speed is finding how quickly they can do a task, or how many tasks they can complete in a given time.
In other words, while these assessments are looking at many of the same concepts, they are not exactly identical.
Floor & Ceiling
As we start looking at some specific assessments, there is one more thing we should discuss. This is the idea of a floor and ceiling for these assessments. The floor is the lowest IQ the assessment can measure, and the ceiling is the highest. Some of the assessments have a lower floor, meaning they can measure down to a lower level of intelligence. While others have a higher ceiling, so they can measure higher intelligence more reliably.
Merrible-Palmer Scale of Mental Tests
The Merrible-Palmer Scale of Mental Tests can be used for the youngest ages of the assessments we’re reviewing. This can be used for those who are infants one month of age up to children below the age of 7. It takes about 45 minutes to administer.
Wechsler Preschool and Primary Scale of Intelligence (WPPSI)
Next we have the Wechsler Preschool and Primary Scale of Intelligence, which is in its fourth edition. This is for those who are 2 years and 6 months old up to the age of 7 years and 7 months. The administration time will vary by the age of the person being evaluated, but can range from 30 to 60 minutes.
Wechsler Intelligence Scale for Children (WISC)
Currently in its fifth edition, the Wechsler Intelligence Scale for Children, or WISC, is used for children between the ages of 6 to 16 years and 11 months. Administration for this test is around 60 minutes.
Wechsler Adult Intelligence Scale (WAIS)
Then we have the WAIS, or the Wechsler Adult Intelligence Scale. This assessment is currently in its fourth edition. This can be administered to those ages 16 to 90. It assesses ten subject areas and the test takes between 60-90 minutes. The floor for this assessment is an IQ of 40, and the ceiling is an IQ of 160. Because of the floor and ceiling for this assessment, many believe it is best for those with typical intelligence.
Stanford-Binet Intelligence Scales
Finally, we have the Stanford-Binet. This is the test that was originally based on the Binet–Simon Intelligence Test that was given to children in Paris. Their test was then brought over to the United States in 1916 by Lewis M. Terman. He worked at Stanford University and they started adapting the assessment to children in the U.S., including translating it to English. It has since evolved into the Stanford-Binet that is used today.
The Stanford-Binet Intelligence Scales is in its fifth edition. It has an age range of 2 to 85 plus. Depending on age, the person may receive an abbreviated or full version of the test. The time needed for this assessment will vary, but is around 5 minutes per subtest. The Stanford-Binet has a lower floor than other assessments, and a higher ceiling with a top IQ of 180. Because of the lower floor and higher ceiling than other assessments, it is believed to be best for assessing those in the extremes of intelligence.
A Note on Training
Keep in mind, to administer the assessments we just reviewed, you must have a doctorate degree and the other necessary qualifications to give each assessment.
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