The science of IQ: How it’s calculated and what it measures

Ever caught yourself wondering about the magic and mystery that lies within our brains? 

I know most of us have.

And one of those mysteries we often bump into is the Intelligence Quotient, or as most of us know it, IQ.

Now, you might ask, “What’s this IQ all about? Can the human mind be quantified?”

Well, I’m glad you’re here, because we’re about to embark on a journey through the fascinating labyrinth of IQ. Let’s talk about what it is, how it’s calculated, and what it measures. 

What is IQ?

IQ, short for Intelligence Quotient, is a measure that’s used to gauge our cognitive abilities. It’s a bit like an academic score but for our brains. 

Now, the term “IQ” was coined way back in the early 1900s by a German psychologist named William Stern.

The original concept was quite simple: it was about comparing our “mental age” (how our brain performs) to our actual “chronological age” (how old we are). The higher your mental age compared to your actual age, the higher your IQ score. Neat, right?

But it turned out to be a bit more complex than that.

Today, the American Psychological Association (APA) gives us a slightly different take on IQ. They describe it as a representation of a person’s performance on a set of tasks that have been designed to measure a person’s cognitive abilities.

In simpler words, an IQ test doesn’t just ask, “How smart are you?” Instead, it’s more like, “How well can you solve these specific problems?” 

And here’s the thing: these tasks aren’t just about what you know. They’re about how you think.

What does IQ measure?

Here’s where it gets even more interesting: 

IQ isn’t a measure of knowledge. When you’re taking an IQ test, the score you get shows more about your ability to learn, understand, and solve problems than your actual knowledge.

In simple terms, IQ shows your overall cognitive abilities, instead of what your actual intelligence looks like. 

So, what exactly does an IQ test measure? 

Here are some of the core areas:

  • Verbal comprehension – This is all about how well you understand and use language. It’s not just about big words. It’s about communication and understanding context.
  • Perceptual reasoning – Ever tried to solve a jigsaw puzzle? That’s perceptual reasoning in action. It’s your ability to look at parts and see the whole picture, literally and metaphorically.
  • Working memory – IQ score isn’t just about remembering a list of items. Instead, it shows how well you can manipulate and use information in your mind.
  • Processing speed – This is about how quickly you can understand and respond to information. Therefore, we can say IQ score is somehow like the speedometer in your brain.

But let’s not forget that this is just a snapshot. 

Contrary to the common myth about IQ, in reality, IQ tests don’t measure everything about our intellect. For instance, this simple score doesn’t tell you anything about your creativity, emotional intelligence, or social understanding.

Still, IQ scores do offer some useful insights — certain aspects of our cognition. And here’s where the magic of numbers comes into play:

How can you calculate an IQ score?

Now, you might be wondering, how do we distill all these complex cognitive processes into a single number? 

Well, it boils down to some interesting mathematical wizardry, based on two key concepts: mental age and chronological age.

The standard method of calculating an IQ score is by using this formula:

IQ = (Mental Age / Chronological Age) x 100

Let’s break it down.

Mental age

Think of mental age as your intellectual maturity. It’s like a snapshot of how your cognitive abilities stack up compared to others. 

When psychologists talk about mental age, they’re referring to the level at which your brain is functioning, compared to the average performance of others in your age group.

Imagine you’re a 10-year-old who just aced an IQ test designed for 12-year-olds. In this case, your mental age would be 12.

So, mental age is  a way of saying, “Hey, your thinking skills are on par with the average 12-year-old.”

Chronological age

Meanwhile, your chronological age is just a fancy term for how old you actually are (you know, how many candles were on your last birthday cake). 

In the realm of IQ, it acts as a standard to which your mental age is compared.

So, in our scenario above, your mental age is 12, while your chronological age is 10. Plugging these into our formula, we get:

IQ = (12 / 10) x 100 = 120

Voila! An IQ score of 120.

Common IQ tests

The science of IQ How its calculated and what it measures 2 The science of IQ: How it's calculated and what it measures

Even though I’ve just simplified the concept of IQ with a basic equation, in reality, assessing human intelligence is no easy task

Over the years, several different IQ tests have been developed, each with its own unique way of measuring cognitive abilities. 

The following are some of the most common and empirically validated ones that are used today:

  • Stanford-Binet Intelligence Scales 

This test is a direct descendant of the original IQ test, developed by Alfred Binet. Today, it’s been refined and expanded to assess various cognitive areas such as verbal reasoning, quantitative reasoning, visual-spatial processing, and working memory.

  • Wechsler Adult Intelligence Scale (WAIS)

A heavyweight in the IQ testing field, the WAIS delves into verbal comprehension, perceptual reasoning, working memory, and processing speed. It’s used widely and holds a significant amount of respect in the psychological community.

  • Raven’s Progressive Matrices

This test stands apart from others by focusing exclusively on non-verbal reasoning. It’s designed to be ‘culture-fair,’ meaning its questions aim to minimize the impact of language and cultural familiarity.

  • Woodcock-Johnson Tests of Cognitive Abilities

A comprehensive suite of tests, the Woodcock-Johnson explores knowledge, comprehension, memory, and speed. It’s a common choice in educational and professional settings.

  • Differential Ability Scales (DAS)

The DAS offers a more nuanced approach to measuring cognitive abilities, emphasizing the understanding and application of learned material rather than rote learning. It assesses a broad range of cognitive skills, providing detailed profiles of strengths and weaknesses.

Despite the diverse range of IQ tests available, each offering its own unique lens to view our cognitive abilities, it’s critical to remember that they’re just tools. 

Again, they can provide insights, but they don’t wholly define us. 

And that’s indeed why standard IQ tests have been subject to plenty of controversies and misinterpretations among psychologists and researchers over the past century and up to now.

The great IQ debate: controversies and misinterpretations

Delving deeper into the realm of IQ, we encounter a world of controversy and misinterpretations. 

The reason is simple:

While IQ tests can offer a snapshot of cognitive abilities, they often miss out on the full panorama of human intelligence, which includes aspects like emotional intelligence, creativity, and practical skills.

What’s more, cultural bias is a sticking point in IQ assessments. 

This means that IQ tests can accidentally favor individuals from certain backgrounds, causing potential imbalances in results. 

A classic illustration of this can be found in the work of Richard E. Nisbett, Ph.D. As he found out, cultural context significantly influences intelligence measures, pushing for a need to reassess how we conduct and interpret these tests. 

His work underscores the importance of ‘culture-fair’ testing, where the influence of cultural and linguistic familiarity is minimized to ensure a more balanced assessment.

And let’s not forget about the misinterpretations that often accompany IQ scores:

These scores, although useful, are not set in stone. They can fluctuate based on various factors, including education, environment, and personal motivation.

So, while an IQ score can offer some insight into our cognitive abilities, it’s not a definitive measure of our intelligence

It’s just one facet of the multi-dimensional and ever-evolving human intellect.

Beyond the numbers

So, here we stand at the end of our exploration into IQ. 

Hopefully, you now understand that IQ, as intriguing as it is,  only shows a small part of our total brain power.

It’s a useful tool that gives us some information about our thinking skills, but it doesn’t tell the whole story about our intelligence.

Remember: no test can capture the multifaceted marvel that is you. You are more than a number. You are a combination of strengths, talents, and capabilities. You have the power to learn, grow, and excel in countless ways.

So keep exploring your unique abilities and strengths. You are not just an IQ score, you’re a delightfully complex person with various talents and potential.

Picture of Nato Lagidze

Nato Lagidze

Nato is a writer and a researcher with an academic background in psychology. She investigates self-compassion, emotional intelligence, psychological well-being, and the ways people make decisions. Writing about recent trends in the movie industry is her other hobby, alongside music, art, culture, and social influences. She dreams to create an uplifting documentary one day, inspired by her experiences with strangers.

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