When it comes to understanding intelligence, there’s no single definition that fits everyone. Psychologists have debated for decades whether intelligence is just one general ability (often called “g-factor”) or a mix of independent skills. One of the biggest game-changers in this debate was Louis Thurstone, an American psychologist who, in the early 20th century, introduced the idea of Primary Mental Abilities (PMAs).
Instead of seeing intelligence as a single, overarching score, Thurstone argued that it’s a collection of different cognitive strengths. His theory still matters today, especially in education, psychology, and talent development. So, let’s break it all down.
The Big Seven: Thurstone’s Primary Mental Abilities
Thurstone identified seven key mental abilities that make up intelligence. Think of them as different “superpowers” in your brain—some people are stronger in certain areas while weaker in others, and that’s totally normal.
- Verbal Comprehension – If you’re great at understanding and using language, this is your strength. Think strong vocabulary, reading comprehension, and making sense of complex ideas.
- Word Fluency – Ever win a word scramble or crush at rhyming games? This ability is all about how quickly and creatively you can come up with words.
- Number Facility – Your inner math whiz. If you find calculations easy or enjoy working with numbers, you shine here.
- Spatial Visualization – The ability to picture things in 3D. If you’re good at solving puzzles, navigating unfamiliar places, or designing things in your head, this one’s yours.
- Memory – Your recall ability. If you ace trivia nights or can remember lists and facts effortlessly, memory is your strong suit.
- Perceptual Speed – The ability to quickly spot patterns, differences, or details. Great for editors, detectives, and those who excel at “spot the difference” puzzles.
- Reasoning – The skill of logical thinking and problem-solving. If you enjoy strategy games or figuring out how things work, you’re using this ability.
These abilities don’t all develop equally in everyone, which explains why some people are amazing with numbers but struggle with words—or vice versa. Thurstone’s model highlights the diversity of intelligence rather than squeezing everyone into the same box.
How Did Thurstone Investigate General Intelligence?
So, if intelligence isn’t just one big thing, how did Thurstone prove it? He designed a series of tests to measure different mental skills and then gave them to a large group of children.
The goal? To see whether people who scored high on one test (say, a math-based test) also scored high on another (like a verbal test). If intelligence was truly a mix of independent skills, the test results should have shown no significant connection between different abilities. But Thurstone found something interesting—there were positive correlations between certain abilities, meaning that while they were distinct, they were also connected in some way.
This finding suggested that there is a general intelligence factor (G) mixed in with specific abilities. In other words, intelligence is both diverse and interconnected, which is why some people excel across multiple areas, while others have more specialized strengths.
How Intelligence Tests Like the WAIS Measure These Abilities
Today, intelligence tests like the Wechsler Adult Intelligence Scale (WAIS) have been shaped by ideas from Thurstone and other psychologists. These tests don’t just spit out a single IQ score—they measure different cognitive skills to give a more complete picture of intelligence.
Here’s how WAIS evaluates primary mental abilities:
- Verbal Comprehension – Measures understanding of spoken and written language, including vocabulary and the ability to explain concepts.
- Perceptual Reasoning – Assesses non-verbal problem-solving, such as recognizing patterns and solving puzzles.
- Working Memory – Tests short-term memory, such as recalling number sequences or rearranging information in your mind.
- Processing Speed – Looks at how quickly and accurately a person can complete simple tasks, like matching symbols under time pressure.
By measuring these different aspects, intelligence tests today align with the idea that intelligence isn’t just one thing—it’s a combination of multiple cognitive strengths.
What Do Different Theories Say About Intelligence?
Psychologists don’t always agree on what intelligence actually is. Here’s how different theories define it:
- Psychometric Theories – Intelligence is measurable through standardized tests. (Think IQ tests and the work of Binet and Terman.)
- Cognitive Theories – Focuses on how intelligence develops through learning and problem-solving (like Piaget’s theory of cognitive development).
- Multiple Intelligences Theory – Howard Gardner’s idea that intelligence isn’t just about logic and language—it includes musical, spatial, interpersonal, and other forms of intelligence.
- Emotional Intelligence – Daniel Goleman’s theory that being emotionally aware and socially skilled is a form of intelligence.
- Triarchic Theory – Robert Sternberg’s idea that intelligence has three parts: analytical (problem-solving), creative (thinking outside the box), and practical (adapting to situations).
Thurstone’s PMAs fit into this bigger discussion, reinforcing the idea that intelligence is complex, multi-layered, and far from one-size-fits-all.
How Do We Measure Intelligence Today?
Measuring intelligence has come a long way, and it’s no longer just about getting a single IQ score. Modern intelligence tests consider multiple abilities, including:
- Verbal & Word Fluency – How well you understand and use language.
- Numerical Ability – Your skill with numbers and logic.
- Spatial Reasoning – Your ability to think in pictures and manipulate objects mentally.
- Memory & Perceptual Speed – How quickly and accurately you recall and process information.
Thurstone’s research helped shape the way intelligence tests are designed today, influencing tools like the WAIS, Stanford-Binet, and other cognitive assessments.
The History of Intelligence Research
The study of intelligence has a long history, with contributions from Alfred Binet, Lewis Terman, and William Stern.
- Alfred Binet – Developed the first practical intelligence test in the early 1900s to identify students who needed extra help.
- Lewis Terman – Adapted Binet’s test into the Stanford-Binet Intelligence Scale and introduced the IQ score.
- William Stern – Coined the term “IQ” and introduced the formula for calculating intelligence (mental age ÷ chronological age × 100).
These pioneers laid the foundation for modern intelligence research, which later evolved into theories like Thurstone’s PMAs.
The Extremes of Intelligence
Intelligence exists on a spectrum. At one end, we have gifted individuals, and at the other, those with intellectual disabilities.
High Intelligence (Giftedness)
People with exceptionally high intelligence often have:
- Exceptional problem-solving skills
- Advanced memory and learning abilities
- High creativity and innovation
While gifted individuals excel in many areas, they can also face challenges like social isolation or pressure to meet high expectations.
Intellectual Disabilities
Individuals with intellectual disabilities may have:
- Learning and developmental delays
- Difficulties with reasoning and problem-solving
- Challenges in social interactions
Support and personalized education play a huge role in helping people at both ends of the intelligence spectrum thrive.
Why Thurstone’s PMAs Still Matter
Thurstone’s theory of intelligence was ahead of its time. By recognizing multiple mental abilities, he challenged the idea of a single IQ score defining intelligence. His work still influences modern education, talent development, and intelligence research.
Understanding intelligence as multidimensional helps us appreciate that everyone has unique cognitive strengths. Whether you’re strong in reasoning, memory, or verbal fluency, there’s no single “right” way to be intelligent—and that’s pretty empowering.
What do you think? Which of the seven primary mental abilities do you feel strongest in? Let’s talk! 😊
