CHC Theory, Cognitive Assessment, Principles of assessment of aptitude and achievement

Why do IQ tests measure vocabulary?

If Lexical Knowledge (understanding of words and their uses) is simply memorizing the definitions of fancy words, then, at best, it is a trivial ability valued by academics, pedants, and fuddy-duddies. At worst, its elevation by elitists is a tool of oppression. There is some truth to these views of Lexical Knowledge but they are myopic. I will argue that vocabulary tests are rightfully at the center of most assessments of language and crystallized intelligence. Some words have the power to open up new vistas of human experience. For example, when I was thirteen, learning the word “ambivalence” clarified many aspects of interpersonal relationships that were previously baffling.

A word is an abstraction. The need for labels of simple categories is perfectly clear. Knowing the word anger (or its equivalent in any other language) frees us from having to treat each encounter with the emotion as a unique experience. Being able to communicate with others about this abstract category of experience facilitates self-awareness and the understanding of interpersonal relations. We can build up a knowledge base of the sorts of things that typically make people angry and the kinds of reactions to expect from angry people.

It is less obvious why anger has so many synonyms and near-synonyms, some of which are a bit obscure (e.g., iracund, furibund, and zowerswopped!). Would it not be easier to communicate if there were just one word for every concept? It is worthwhile to consider the question of why words are invented. At some point in the history of a language, a person thought that it would be important to distinguish one category of experience from others and that this distinction merited a single word. Although most neologisms are outlived even by their inventors, a few of them are so useful that they catch on and are used by enough people for enough time that they are considered “official words” and are then taken for granted as if they had always existed.[1] That is, people do not adopt new words with the primary goal of impressing one another. They do it because the word succinctly captures an idea or a distinction that would otherwise be difficult or tiresome to describe indirectly. Rather than saying, “Because Shelly became suddenly angry, her sympathetic nervous system directed her blood away from her extremities toward her large muscles. One highly visible consequence of this redirection of blood flow was that her face turned white for a moment and then became discolored with splotches of red.” It is simply more economical to say that “Shelly was livid with rage.” By convention, the use of the word livid signals that Shelly is probably not thinking too clearly at the moment and that the next thing that Shelly says or does is probably going to be impulsive and possibly hurtful.

Using near synonyms interchangeably is not merely offensive to word nerds and the grammar police. It reflects, and possibly leads to, an impoverishment of thought and a less nuanced understanding of the world. For example, jealousy is often used as a substitute for envy. They are clearly related words but they are not at all the same. In fact, in a sense, they tend to be experienced by people on opposite sides of a conflicted relationship. Envy is the painful, angry awareness that someone else enjoys some (probably undeserved) advantage that we covet. Jealousy is the angry, often vigilant, suspicion we may lose our beloved to a rival. Unaware of this distinction, it would be difficult to benefit from or even make sense of the wisdom of Rochefoucauld’s observation that “Jealousy is born with love, but does not die with it.”

Lexical Knowledge is obviously important for reading decoding. If you are familiar with a word, it is easier to decode. It is also obviously important for reading comprehension. If you know what a word means, it is easier to comprehend the sentences in which it appears. It is probably the case that reading comprehension also influences Lexical Knowledge. Children who comprehend what they read are more likely to enjoy reading and thus read more. Children who read more expose themselves to words that rarely occur in casual speech but the meaning of which can be inferred from how it is used in the text. Finally, Lexical Knowledge is important for writing. Children with a rich understanding of the distinctions between words will not only be able to express what they mean more precisely, but their knowledge of certain words will enable them to express thoughts that they might not otherwise have had. For example, it seems to me unlikely that a student unfamiliar with the word “paradox” would be able to write an essay about two ideas that appear to be contradictory at first glance but at a deeper level are consistent with each other.

[1] Of course, dictionaries abound with antique words that were useful for a time but now languish in obscurity. For example, in our more egalitarian age, calling someone a cur (an inferior dog because it is of mixed breed) is not the insult that it once was. It is now used mostly for comedic effect when someone affects an aristocratic air. My favorite example of a possibly soon-to-be antique word is decadent, which is nowadays almost exclusively associated with chocolate.

This post is an excerpt from:

Schneider, W. J. (2013). Principles of assessment of aptitude and achievement. In D. Saklofske, C. Reynolds, & V. Schwean (Eds.), Oxford handbook of psychological assessment of children and adolescents (pp. 286–330). New York: Oxford.


6 thoughts on “Why do IQ tests measure vocabulary?

  1. Manuel Cruz says:

    While it is true that words are powerful tools, that language is an art, and that the good use of words gives us more context and can inspire us feelings, that is not the reason IQ tests measure vocabulary.
    The reason is that in the original IQ tests, men had higher scores than women, with women falling far below the supposed population mean (arbitrarily marked as 100). This was contrarian to leftist dogma, and because leftists do not really believe in science, when truth hurts they reject it, pushing for a “fix” to the tests so that the mean of women would also fall at 100 IQ, as this feels “numerologically perfect” (magical thinking).
    As little girls read more books than boys (not the kind of books that make you more intelligent, sadly), the logic move to improve girl scores was to replace questions measuring real intelligence (pattern recognition and abstract thinking, among others) with questions measuring vocabulary (memory), until the means of both girl and boy populations were balanced at the same point.
    As this is a hack, not based on any solid science research on intelligence, it is expected that the means of boys and girls will diverge as social habits change. At that point, there will be a strong push from academia to either get rid of IQ tests, or change them so that they do not measure intelligence at all.
    The usefulness of science is that it exposes truth. Faking reality to protect flawed dogma does a disservice to everyone. Higher education used to mean something, now it doesn’t. Psychology and sociology have never been sciences, they are sophistry, and deserve zero respect.

    • Hi Manuel,

      Thank you for your thoughts. I think that further study may cause you to update your opinion. Whatever the motives of the first researchers to include vocabulary in IQ tests, sex differences in vocabulary are negligible (see p 10 in or find pages 535-536 in Arthur Jensen’s book The g Factor if you want a decidedly non-leftist take on the matter).

      I think also you would do well to broaden your notion of what “real intelligence” is. No one has been able to articulate a compelling definition of “real intelligence” in over 100 years. Most of us no longer try. We accept that intelligence is a broad concept that encompasses many things (see Box 1 in my paper here Pattern recognition and abstract thinking are no doubt important components of intelligence, but verbal ability is important as well. In fact, verbal ability tests (such as vocabulary tests) are generally stronger predictors of success than pattern recognition and abstract reasoning tests, in part because good verbal ability tests incorporate abstraction in them.

      Vocabulary tests correlate with the general factor of intelligence better than almost any other kind of test (see p. 278 in A well-designed vocabulary test measures reasoning to a much greater degree than you might expect. Memory has surprisingly little to do with it after factoring out understanding (i.e., we tend to remember that which we understand). Very little of your vocabulary is memorized. Almost all of it is inferred from context. Intelligence is required to infer the correct meaning. One of the easier ways to detect low intelligence in casual conversation is to note the absence of complex vocabulary and/or the misuse of words. Verbal tests like vocabulary also have unique components of ability that are important predictors of a wide range of important academic and occupational outcomes.

      Furthermore, I think you should reexamine your beliefs about the power that ideology has in psychology. To put it mildly, intelligence researchers do not have a reputation for altering their findings to align with leftists’ preferences. Ask any leftist what he or she thinks of IQ research, and see what happens. There were and are many non-leftist psychologists who study intelligence, and there is no push among them to remove vocabulary tests from IQ tests. If you wish to do some research to persuade the field to remove vocabulary from IQ tests, you are welcome to present your case.


      Joel Schneider

      • Prasanga says:

        I’m still confused about the study. I understand and accept the correlation between vocabulary and the g factor. I also understand that it is an essential part of crystallized intelligence. And if I’m not mistaken, fluid intelligence also correlates with vocabulary. Yet, I fail to understand why this correlation exists. A person who used to read a lot will see his vocabulary increase, regardless of his intellect.
        I didn’t read a lot of books as a child and I came to the states at the age of 10 with little knowledge in English. I went to honor classes only after a year. I just turned 16 and I scored in the 90th percentile in the English section of the PSAT. Although not that impressive, it is definitely more than one standard deviation from the average. I honestly don’t believe my vocabulary skills are that good. Yet, I have done fairly well in verbal tests, whether it be the PSATs, Regents, and state tests without much effort. Am I an exception? Or is my arrogance preventing me from accepting my lower intellect?

      • I am guessing from your PSAT (and this short writing sample) that your vocabulary is better than you think. Nevertheless, there are always many exceptions to every trend. There are brilliant people with middling vocabularies, and there are word aficionados with average intelligence.

      • Alex Gunz says:

        What a fantastic reply – better than the actual original blog post. You should post it up as a new one itself.

        While challenging nothing that you have said, one slight elision (tee hee, that one I actually did straight up memorize back in the GRE days) is that while words are OFTEN invented to catch new meanings, they are also often invented for other reasons, such as to be social markers. I’ll age myself here, but when I was growing up young people started using “wicked” to mean “good”… not becasue they needed a new concept, but as a social marker from the olds (and there is a quasi-neologism from an even younger generation).

        Now I suspect that this will do little to expand people’s active vocabulary size, and is unlikely to be tested on IQ measures anyway (“sweet:awesome as…”)…. but what can you do 🙂

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