How do IQ tests measure crystallized intelligence

How do you actually define intelligence?

How do you actually define intelligence?

Intelligence tests and their informative value are controversial. The tests are usually used to measure and compare skills and competencies. Psychologists use a wide variety of theories and models for this.

Some say about the relationship between intelligence and the intelligence test: Intelligence tests are nothing more than disguised prejudices and measure everything possible, just not intelligence. The other: Intelligence is what the intelligence test measures. And quite a lot of people say: We don't even know what intelligence is. The latter in the knowledge that they can very well distinguish an intelligent person from a less intelligent person.

Do we need to know what intelligence is in order to measure it? The answer may come as a surprise: no, we don't need to know. But we have to state what we are measuring. The psychologists say: We measure to compare. Intelligence tests should always answer a clear, specific question. Just not: How intelligent am I? Rather, is it appropriate for the slightly nervous Hans to skip a class? Or: Will Fritz manage to successfully complete a university course? That is why psychologists can claim that intelligence tests are one of the most reliable we have. Because their predictive power is great.

American and British pioneering work

The correlation between the measured value and the individual's success in life is very high. If the test says: Yes, Fritz can do it, then the probability that Fritz will then pass the master's degree is 80 percent and higher. IQ tests and later income also show a high correlation.

Of course, the skills and competencies to be measured stem from certain ideas or theories about intelligence. Key inputs came from three prominent psychologists. The British Charles Edward Spearman (1863-1945) noticed that the results of various tests showed a positive correlation. From this he concluded that there must be a general intelligence factor. He called it “general intelligence” or “g-factor”. He explained the differences in the tests with special factors: "s-factors" (linguistic, numerical, figural - depending on the test).

The American Louis Leon Thurstone (1889–1955) expanded Spearman's “two-factor theory” and reduced intellectual performance to seven “primary factors”: Verbal competence, fluency (quick production of a word in a certain situation), numeracy, spatial imagination, Retention (short-term memory), speed of perception and reasoning.

The British-American personality psychologist Raymond Bernhard Cattell (1905-1998) differentiated the model and made it hierarchical. He saw two overriding factors: “fluid intelligence” (gf) and “crystalline intelligence” (gc). Cattell understood “fluid” as the ability to adapt to new situations, to solve new problems without being able to fall back on acquired knowledge, and to recognize new patterns and analogies. “Crystalline” means being able to access what you have learned and apply skills. "Crystalline intelligence" is cumulative and lasts for a long time - and of course it grows faster, the greater the "fluid intelligence".

You need a reliable scale

The Berlin Structure Model (BIS) integrated the suggestions and differentiated content-related (pictorial, verbal, numerical) and operational skills (processing speed, memory, ingenuity, processing capacity), which are mutually dependent and supportive. Measuring and comparing needs a reliable scale. And this doesn't just happen. The results of intelligence tests have to be "normalized" using mathematical methods in order to be meaningful and comparable. The intelligence in a population is normally distributed. Where most people meet, the value 100 is marked. One third each is between 85 and 100 and between 100 and 115. 130 and more points (gifted) only reach around two percent of the population. Again: this has been set up with mathematical tricks. And one more thing: The most intelligent are those people who are happy with their life, whatever their IQ.