Can you really measure intelligence?

Whether you like it or not, we're all part of a social system that tends to define people by intelligence. Everything from getting into a university, to getting a job tests you for some facet of intelligence. Some pass, others fail. Round pegs don't fit in square hole.

But are these tests really fair? Are they actually measuring a person's intelligence? Is everyone supposed to be intelligent in the same manner?

Once again this would be one of my more fact-rich, self-reference posts with a lot of names and details. If you're interested in an in-depth article on IQ and intelligence; keep reading - I've made it as interesting as I could.

Intelligence is the ability to acquire and apply knowledge and skills. It allows us to deal adaptively with our environment.

Our earliest measure of intelligence came in the form of a reaction speed test. Sir Francis Galton believed reaction speed, sensory acuity and skull size were related to intelligence. We now know that intelligence is a far more complex measurement than this. But even at the time it fell into disfavour as it didn't align with the socially accepted concept of intelligence, which came in the form of occupational success. But you've got to credit him for creating enough interest in the field which lead to the development in intelligence tests we still use today.


Early tests of intelligence

Alfred Binet believed that intelligence was a collection of higher order abilities that developed with age at a constant rate. Based on this assumption he created a standardized test using various cognitive abilities. He used this test to come up with the testing score of "Mental Age."

Following this, William Stern developed on the idea of mental age to come up with the IQ score which we're all familiar with. Simply put:

IQ = mental age / actual age

But using the mental age actually only works with children. If you take a look at the equation you'll notice why it quickly break down when the actual age increases, which is why we don't use the mental age when calculating IQ scores in the present. To solve this David Wechsler came up with a deviation IQ based on a z-score. So now we can graph IQ as shown below. It's calibrated to always have a mean IQ of 100 in the population.

IQ Score Standard Deviation

When you come up with a test for something like intelligence, a lot of factors need to be considered to ensure the test is fair, valid and reliable.

  1. Is the test measuring what it should be measuring?
  2. Is the test culture-fair (does the test require culture specific knowledge to answer)?
  3. Could you re-test and get a stable score over time?

IQ scores are far from how people actually do in life. Yet it's still widely used. Understand that intelligence is a socially constructed concept. The attributes of intelligence depend on the society and environment you're in.

For example, if you drop a business graduate in the Amazon rainforest, more likely than not they'd be dead within the week. On the other hand, if you drop off a Native–who's lived their entire life in the Amazons–in New York! They'd be pretty helpless too. They're smart in their own enviroment.

Over the years we've come to measure intelligence using various different metrics. The most popular of which is the IQ score, and there're many different tests to measure it. You probably already have come across the popular Raven's IQ test that pops up on social media frequently.

Raven’s Progressive Matrices

This test consists of a number of non-verbal tasks, where the subject is shown a number of patterns which they are required to decipher. It is a very good example of a non-culture specific measure of intelligence.

Raven’s Progressive Matrices


Psychometric approach to intelligence

This is the statical study of psychological tests. This would be where we ask the questions: is intelligence a general capacity? Or is it the result of a combination of several specific mental abilities?

Overtime, many different people have come up with various tests and measurements for intelligence. They all measure various mental abilities or groups of abilities to come up with some comparable score for it.

It's important to note that measures of intelligence have a very rich history. Many psychologists have suggested numerous measurements and theories. Here're some of them:

Charles Spearman

He believed intelligence is based on one general skill. He called it the g-factor, this is what many people refer to when they say 'intelligence'. The g-factor is known for predicting job success even better than scores measuring job-specific abilities.

Louis Leon Thurston

He is responsible for the standardized mean and standard deviation of IQ scores we use today. He believed that intelligence is more complex than a g-factor. In fact he believed there were seven independent primary mental abilities1.

  1. Spacial ability
  2. Verbal comprehension
  3. Word fluency
  4. Number facility
  5. Perceptual speed
  6. Rote memory
  7. Inductive reasoning
Raymond B. Cattell and John Horn

They developed the Fluid and Crystallized Intelligence2 theory. They believe these two were the sub-types of the g-factor.

Crystallized intelligence involves the application of prior knowledge whereas Fluid intelligence is about the capacity to reason and solve novel problem, independent of any prior knowledge.

John Carroll

He came up with the Three-stratum theory of cognitive ability. The three layers are denied and narrow, broad and general cognitive ability.

  • Stratum I: Includes 70 highly specific cognitive abilities
  • Stratum II: 8 broad intellectual factors
  • Stratum III: General intelligence (g)

Cognitive approach to intelligence

These theories try to explain why mental abilities vary among individuals.

Robert Sternberg

He believed that intelligence should be studied in a broader way in order to include other parts of intelligence. Some people are book-smart, and this tends to be what we measure through most intelligence tests. However there're people who score low on these tests that are street-smart or creative.

He came up with the The Triarchic Theory3 of intelligence:

  • Metacomponents: these are higher order processes used to plan and regulate task performance.
  • Performance component: Actual mental processing used to perform tasks.
  • Knowledge acquisition components: Learning from experience.

He also created the three classes of intelligence:

  • Analytical intelligence: academic intelligence
  • Creative or synthetic intelligence: the skill of dealing adaptively with novel problems
  • Practical intelligence: the skill of dealing withe everyday life by drawing on existing knowledge and skill

Howard Gardner

He proposed the Theory of Multiple Intelligences4. Rather than seeing intelligence as a single general ability, he broke it down to several independent intelligences. He proposed this model in his book Frames of Mind: The Theory of Multiple Intelligences in 1983.

Intelligence modalities:

  • Linguistic: the ability to use language well
  • Logical–Mathematical: the ability to reason mathematically and logically
  • Visual–spatial: the ability to solve spatial problems
  • Musical: the ability to perceive pitch and rhythm
  • Bodily–kinesthetic: the ability to control body movements and skillfully manipulate objects
  • Interpersonal: the ability to understand and relate with others
  • Interpersonal: the ability to understand oneself
  • Naturalistic: the ability to understand phenomenon in the natural world
  • Existential: ability to ponder questions about the meaning of life
Emotional Intelligence

This is the capability to recognize your own, and other people's emotions5. Proponents suggest that emotionally intelligent individuals form stronger bonds with others and have the ability to modulate their emotions to avoid negative feeling. They are even successful towards accomplishing long-term goals.

The term came to popularity through the book Emotional Intelligence by Daniel Goleman in 1995.


Here're some different methods of testing you should know about.

Aptitude vs Achievement

Achievement tests measure developed skills or knowledge, the most common type being standardized tests measuring knowledge at a given grade (like school). An aptitude tests on the other hand measures the ability to learn certain skills. But a problem with the latter being that it's harder to test such skills compared to something which is learnt. One might also say the latter is a much fairer assessment of intelligence.

Static vs Dynamic

Static test are standardized tests where everyone is being measure on the same ability in the same environment. This contrasts to dynamic testing which includes the tester providing feedback to the subject and then measuring their ability to improved based on it. This is very useful for testing people without equal education opportunities.


Did you know IQ scores increase by about 3 points every decade? This is likely due to improved education, access to knowledge and better technology and standards of living. However, note that our system of measurement for IQ remains unchanged since the mean is always calibrated to be 100, as illustrated in the graph above. IQ is a relative score. We call the continuous increase in IQ the The Flynn Effect after James R. Flynn.


The role of biology in intelligence

There is a modest relationship between IQ and the brain's response to visual and auditory stimuli. Researchers have been able to map the brain areas related to general intelligence6 as shown below.

Brain maps

The image shows a lesion map of g (general intelligence). It's from the research paper Distributed neural system for general intelligence revealed by lesion mapping, which suggests that these regions found support the existing Parieto-frontal integration theory, which says general intelligence depends on the ability of the human mind to integrate different types of processing.


Environment, evolution and genetics in intelligence

Interestingly, men have 6.5x more grey matter than women–leading to better information processing. Women on the other hand, have 10x more white matter resulting in better connectivity.

These differences, and other environmental differences in upbringing result in men being better at things like spatial tasks and target directed skills (throwing). This is no surprising since boys usually play ball growing up, and from as evolutionary perspective: men hunt whereas women raise kids. Making women better at things like precision tasks, perceptual speed and verbal fluency.

It's also interesting to note the difference in intelligence test scores across different ethnic/national groups. For example, Asians have lower verbal scores, but higher math/spatial scores. However, we should always keep in mind these differences could be the result of upbringing. Proper schooling leads to better development of intelligence.


So can you measure intelligence?

Maybe. Maybe not. Should we though?

The tests improve as our understanding of intelligence grow. In fact, part of the problem was people trying to measure it even before they really understood what intelligence is in the first place! There are many different facets to intelligence as we've discussed in detail. Beyond that, there're countless environmental factors that affect how intelligence develops. The real question is: Should we measure intelligence in the first place?

It's a double edged sword. Labelling people with IQ scores can affect expectations in life, specially in children. On the flip side it could also be used to help those with cognitive deficits.

In all honestly, here's what I think about intelligence scores: If you're doing what you love in life then you're the smartest person you could be. If not, what's your next move?

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