IQ is the intelligence that we measure
Everyone agrees: IQ tests don’t measure all kinds of intelligence or ability. Great basketball skill, great musical skill, street-smarts, social intelligence and leadership ability cannot easily be tested in a classroom or office. How would it be done? High IQ is not necessary for success in many careers. I am only writing about intelligence as measured by IQ tests. Inherent intellectual ability and smarts may be greater or less that captured by IQ test results. Factors such as determination, studiousness, self-image emotional state and preparation affect IQ test results, but may not affect inherent intellectual ability.
What does the term “IQ” mean?
Intelligence quotient (IQ) values are not increments of intelligence. They are ranks compared to other individuals. If your IQ test result is 100, it means that half of all tested persons have a lower test result than you do and half a higher one. If your IQ is 130 or more, it means that less than 2.1% of the population has higher IQ test results than you do. If a person’s IQ is 70 it indicates that almost 98% of the population has a higher test results than they do.
Raw IQ test results are adjusted every few years so as to make the above rankings true. The mean (average) result must be 100 and the “standard deviation” must be 15. Since IQ test scores follow a bell curve, therefore, 68.2% of the American population will have an IQ between 85 and 115 (1 standard deviation) and 96% between 70 and 130 (two standard deviations).
The IQ bell curve for IQ is shown below:
The percentage of the population with an IQ is shown by the height of the curve. So, as you can see, only 1/8th of one percent of the American population has an IQ of over 145, or under 55.
Because a child’s performance on IQ tests increases with age, each age of children (through age 15) has its own IQ distribution.
Uses of IQ Tests
IQ tests have been used by some to stereotype people, to hold down races and women, and to justify eugenics – the programs to breed and cull our own species, used successfully and acceptably in Singapore, but disastrously by Hitler. In my opinion, if some use IQ for destruction, that is not the fault of the tool. but of the user. Many useful tools, can be used to harm.
Intelligence tests help determine who should go into the military and in what roles. They help put soldiers into positions where they can succeed. IQ tests help determine who should skip or hold back a grade, who should consider going to university and to which university. They help to determine, not always accurately, which children need remedial help or would benefit from advanced classes and which adults need assisted living. While IQ tests don’t measure all the skills required to succeed, they can help young people choose careers for which they are well-suited. (Source 1 discusses at length the IQ required for various careers, and why testing for this is important.)
Furthermore, high IQ test scores are useful to predict success in university studies and in intellectually demanding and competitive professions such as engineering, finance, law, medicine, and scientific research. Thus, IQ test results – though not an indication of pure intellectual ability – are indeed an excellent indication of the capacity to apply intellectual ability in competitive professions.
Are IQ Tests Fair?
At least within Western cultures, IQ tests have been found to be reproducible and to not discriminate against minorities. (Sources 2 3
All of the several main IQ tests are individually administered, and they all give similar results, with an error that is usually not more than 3 IQ points up or down, and almost never more than 9 points up or down. Written tests such as SATs and ACTs that are administered to groups, also indicate IQ, although they are not based upon as many capabilities and give much more importance to previous learning and preparation. The results are also reproducible, (Sources 4 5).
IQ tests are less accurate in distinguishing IQs above 130 and below 70. The questions are designed for average populations, and are not difficult enough or easy enough to distinguish between takers at the extremes of IQ. (Source 6)
The Categories of IQ:
The most commonly used IQ Test for adults and older adolescents is the Wechsler Adult Intelligence Scale, or WAIS, Version IV, first published in 1959. It takes about an hour or an hour and one-half for a trained practitioner to administer. (For greater detail, see Source 7)
Crystallized intelligence:
Crystallized intelligence is defined as the ability to cumulate knowledge and vocabulary and use it. (Source 8 discusses the types of intelligence). Crystallized intelligence increases through most of youth and middle age, then tends to decline after age 65. The following sub-tests measure crystallized intelligence: Verbal Comprehension, word similarities or differences, vocabulary definition, and general knowledge (And as a supplemental test, comprehension.)
Fluid Intelligence:
Fluid Intelligence is defined as the ability to solve unfamiliar problems, to reason abstractly, to recognize patterns. It typically peaks in young adulthood and then declines steadily. The following subtests measure fluid intelligence:
Perceptual Reasoning Subtests, where two-dimensional designs must be copied using three-dimensional blocks, where patterns must be identified, where a choice of three geometric forms must be combined to form a specified design. (And as a supplemental test, picture completion and using weight symbols on a balance.)
Working Memory Subtests, where digits are read and must be repeated, in the same order, then in backwards order; and timed tests of simple arithmetic problems to be solved in one’s head. (And as a supplemental test, putting digits or letters read orally into the proper sequence.)
Processing Speed Subtests, where, first, given a group of symbols, within a time span, one must determine if any of them are in another group of symbols. And second, coding, where given correspondences between numbers and symbols one must translate from the numbers to the symbols. (And as a supplemental test, the timed crossing out from a collection of symbols certain specified symbols.)
The IQ sub-tests correlate:
In the Wechsler, all the subtests of intelligence correlate, generally by by 50 – 70 percent (see the Pearson WISC-V-Tech-Manual-Supplement for details). In other words, individuals who do well on one subtests, tend to do fairly well on all of them, and vice-versa. The Wechsler results also correlate highly other versions of IQ tests.
The early 20th century English psychologist Spearman believed that a general intelligence factor contributed to all of the tests, and he called this g. He calculated g from all the subtest results. Scientists who study intelligence typically use g as the measure of how well a person will do on new tasks and abstract reasoning. Though g has been and is influential in studies of IQ, it is nearly identical to IQ (a 95% correlation), and, like IQ, it is merely a statistical result of combining sub-tests. On this website, for simplicity, I will stay with the measurement “IQ”.(Source 9)
Next page: https://iqscience.net/heredity-brain-measurements-and-scans/
- http://www.jordanbpeterson.com/docs/230/2014/21Gottfredson.pdf, Why g Matters: The Complexity of Everyday Life, Linda S. Gottredson, Intelligence 1997 ↩︎
- https://en.wikipedia.org/wiki/Bias_in_Mental_Testing ↩︎
- https://www.brookings.edu/wp-content/uploads/2013/01/9780815746096_chapter1.pdf Christopher Jenks and Meridith Phillips, This is the summary chapter. The entire book, The Black-White Test Score Gap, published by the Brookings Institution in 1998, is available for purchase, including an e-book on Google Play. ↩︎
- http://www.iapsych.com/iqmr/koening2008.pdf ACT and general cognitive ability, Koenig et al, Intelligence, 2008 ↩︎
- https://www.ncbi.nlm.nih.gov/pubmed/15147489 Scholastic Assessment or g? The relationship between the Scholastic Assessment Test and general cognitive ability. Frey & Detterman, Psychological Science 2004 ↩︎
- http://charltonteaching.blogspot.com/2012/07/problems-with-measuring-very-high-iq.html ↩︎
- https://en.wikipedia.org/wiki/Wechsler_Adult_Intelligence_Scale ↩︎
- https://en.wikipedia.org/wiki/Fluid_and_crystallized_intelligence ↩︎
- https://explorable.com/spearman, Lyndsay T. Wilson, Spearman and the Theory of General Intelligence ↩︎