What is Intelligence? Do You Know It When You See It?

It may seem odd, but let’s start our discussion of intelligence with the value of pi, the circumference of a circle divided by its diameter. As you know, the value of pi is always the same: 3.14 … carried out to an infinite, non-repeating sequence of decimals. For our purpose here, it’s just a very long string of numbers in seemingly random order that is always the same. This string of numbers has been used as a simple test of memory. Some people can memorize a longer string of the pi sequence than others. And, a few people can memorize a very long string…

Daniel Tammet, a young British man, studied a computer printout of the pi sequence for a month. Then, for a demonstration organized by the BBC, Daniel repeated the sequence from memory publically while checkers with the computer printout followed along. Daniel stopped over 5 hours later after correctly repeating 22,514 digits in the sequence. He stopped because he was tired and feared making a mistake (Tammet, 2007).

In addition to his ability to memorize long strings of numbers, Daniel also has a facility to learn difficult languages. The BBC also arranged a demonstration of his language ability when they moved him to Iceland to learn the local language with a tutor. Two weeks later he conversed on Icelandic TV in the native tongue. Do these abilities indicate that Daniel is a genius or, at least, more intelligent than people who do not have these mental abilities?

Daniel has a diagnosis of autism and he may have a brain condition called synesthesia. Synesthesia is a mysterious disorder of sensory perception where numbers, for example, may be perceived as colors, shapes, or even odors. Something about brain wiring seems to be amiss, but it is so rare a condition that research is quite limited. In Daniel’s case, he reports that he sees each digit as a different color and shape and when he recalls the pi sequence, he sees a changing “landscape” of colors and shapes rather than numerical digits. Daniel is also atypical among people with autism because he has a higher than average IQ.

Recalling 22,514 digits of pi from memory is a fascinating achievement no matter how it is accomplished (the record is an astonishing 67,890 digits – see Section 6.2). So is learning to converse in the Icelandic language in two weeks. There are people with extraordinary, specific mental abilities. The term “savant” typically is used to describe these rare individuals. Sometimes the savant ability is an astonishing memory or the ability to calculate rapidly large numbers mentally, or the ability to play any piece of music after only hearing it once, or the ability to create artistic drawings or sculptures.

Kim Peek, for example, was able to remember an extraordinary range of facts and figures. He read thousands of books, especially almanacs, and he read each one by quickly scanning page after page. He could then recall this information at will as he demonstrated many times in public forums in response to audience questions: Who was the 10th king of England? When and where was he born? Who were his wives? And so on. Kim’s IQ was quite low and he could not care for himself. His father managed all aspects of his life except when he answered questions from memory.

Steven Wilshire has different savant ability. Steven draws accurate, detailed pictures of city skylines and he does so from memory after a short helicopter tour of the city. He even gets the number of windows in buildings correct. You can buy one of his many city skyline drawings at a gallery in London or online. Alonso Clemons is a sculptor. He also has a low IQ. His mother claims he was dropped on his head as a baby. Alonso creates animal sculptures in precise detail, typically after only a brief look at his subject. The artistry is amazing. Derek Pavacinni has a low IQ and cannot care for himself. He is blind from birth. Derek is a virtuoso piano player. He amazes audiences by playing any piece of music after hearing it only once, and he can play it in any musical style. It is worth noting that Albert Einstein and Isaac Newton did not have any of these memory, drawing, sculpting, or musical abilities.

Savants raise two obvious questions: How do they do it, and why can’t I? We don’t really know the answer to either question. These individuals also raise a core question about the definition of intelligence. They are important examples of the existence of specific mental abilities. But is extraordinary specific mental ability evidence of intelligence? Most savants are not intelligent. In fact, savants typically have low IQ and often cannot care for themselves. Clearly extraordinary but narrow mental ability is not what we usually mean by intelligence.

One more example is Watson, the IBM computer that beat two all-time Jeopardy champions. Jeopardy is a game where answers are provided and players must deduce the question. The rules were that Watson could not search the web. All information had to be stored inside Watson’s 15 petabytes of memory, which was about the size of 10 refrigerators. Here’s an example: In the Category, “Chicks Dig Me,” the answer is: This mystery writer and her archeologist husband dug to find the lost Syrian city of Arkash. This sentence is actually quite complex for a computer to understand, let alone formulate the answer in the form of a question. In case you’re still thinking, the answer, in the form of a question is: Who was Agatha Christie? Watson answered this faster than the humans, and in the actual match, Watson trounced the two human champions. Does Watson have the same kind of intelligence as humans, or better? Let’s look at some definitions to consider if Watson is more like a savant or Albert Einstein.

Defining Intelligence for Empirical Research

No matter how you define intelligence, you know someone who is not as smart as you are. It would be unusual if you have never called someone an “idiot” or a “moron” or just plain dumb, and meant it literally. And, in honesty, you know someone who is smarter than you are. Perhaps you refer to such a person in equally pejorative terms like “nerd” or “egghead,” even if in your innermost self, you wish you had more “brains.” Given their rarity, it is less likely you know a true genius, even if many mothers and fathers say they know at least one.

There are everyday definitions of intelligence that do not lend themselves to scientific inquiry: Intelligence is being smart. Intelligence is what you use when you don’t know what to do. Intelligence is the opposite of stupidity. Intelligence is what we call individual differences in learning, memory, and attention. Researchers, however, have proposed a number of definitions and mostly they all share a single attribute. Intelligence is a general mental ability. Here are two examples:

1. From the American Psychological Association (APA) Task Force on Intelligence:

“Individuals differ from one another in their ability to understand complex ideas, to adapt effectively to the environment, to learn from experience, to engage in various forms of reasoning, to overcome obstacles by taking thought” (Neisser et al., 1996).

2. Here’s a widely accepted definition among researchers:

[Intelligence is] “a very general mental capability that, among other things, involves the ability to reason, plan, solve problems, think abstractly, comprehend complex ideas, learn quickly and learn from experience … It is not merely book learning, a narrow academic skill, or test-taking smarts. Rather it reflects a broader and deeper capability for comprehending our surroundings – ‘catching on’, ‘making sense’ of things, or ‘figuring out’ what to do” (Gottfredson, 1997a).

The concept of intelligence as a general mental ability is widely accepted among many researchers, but it is not the only concept. What evidence supports the concept of intelligence as a general mental ability, and what other mental abilities are relevant for defining intelligence? How do we reconcile intelligence as a general ability with the specific abilities of savants?

The Structure of Mental Abilities and the g-Factor

We all know from our experience that there are many mental abilities. Some are very specific, like spelling or the ability to mentally rotate 3D objects or to rapidly calculate winning probabilities of various poker hands. There are many tests of specific mental abilities. We have over 100 years of research about how such tests relate to each other. Here’s what we know: Different mental abilities are not independent. They are all related to each other and the correlations among mental tests are always positive. That means if you do well on one kind of mental ability test, you tend to do well on other tests.

This is the core finding about intelligence assessment and, as we’ll see throughout this book, it’s the basis for most modern research. Please note this important point: tend means there is a higher probability, not a perfect prediction. Whenever we say that one score predicts something, we always mean that the score predicts a higher probability for the something.

The relationship among mental tests is called the structure of mental abilities. To picture the structure, imagine a three-level pyramid, as shown in Figure 1.1.

At the bottom of Figure 1.1, we have a row of 15 different tests of specific abilities. At the next level up, tests of similar abilities are grouped into more specific factors: reasoning, spatial ability, memory, speed of information processing, and vocabulary. In the illustration, tests 1, 2, and 3, for example, are all reasoning tests and tests 7, 8, and 9 are all memory tests. However, all these more specific factors also are related to each other. Basically, people who score high on one test or factor tend to score high on the others (the numbers in the figure are illustrative correlations that show the strength of relationship between tests and factors; see more about correlations in Textbox 1.1). This is a key finding demonstrated over and over again. It strongly implies that all the factors derived from individual tests have something in common, and this common factor is called the general factor of intelligence, or g for short. g sits at the highest point on the pyramid in Figure 1.1. The g-factor provides a bridge between the definitions of intelligence that emphasize a general mental ability and individual tests that measure (or more accurately, estimate) specific abilities.


What is Intelligence? Do You Know It When You See It? by Manuel Fraga is licensed under a Creative Commons Attribution 4.0 International License.

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