What is IQ? (short) “”—

Introduction

The g factor (also known as the general intelligence factor or general mental ability) is a construct developed in psycho-metric investigations of cognitive abilities. The g-factor is the overarching variable that is theorised to explain the positive correlations between a range of cognitive tasks. For instance, individuals' performance on one type of cognitive task (such as word puzzles) correlates with that person's performance on other kinds of cognitive tasks (such as math problems). Although each task involves using different skills, they both rely on a general intelligence factor.

Composite scores ("IQ scores") are based on many tests and are estimates of an individual's standing on the g-factor. Hereafter we will refer to the g-factor by IQ scores.

See the two diagrams below for the sorts of cognitive abilities which are all separate but all dependent on one's IQ:

Correlation strength between each cognitive ability and IQ:

Note how Vocabulary is its own component in IQ testing. The vocabulary IQ-subtests measure acquired knowledge of word meanings through verbal reasoning, comprehension, and understanding of verbal nuances. All of these skills rely highly on IQ, and although these abilities can be measured by other types of knowledge acquisition, vocabulary is something most people are exposed to at similar degrees. Therefore, vocabulary IQ tests only apply to people who spent their life speaking and learning the language and had a conventional schooling career.

Vocabulary is also known as Lexical Knowledge (understanding of words and their uses), and it is not memorising big, fancy words and using them inefficiently. In fact, being able to put together the right set of words to form a lucid sentence is a better indication of lexical knowledge than obfuscated and overly-complicated writing. Additionally, using near-synonyms interchangeably or using big words incorrectly only reflects a weak understanding of the word and a less nuanced understanding of the world.

Additionally, people adopt new words not to impress one another but because the word succinctly captures an idea or a distinction that would otherwise be difficult to describe every time we want to communicate it. Rather than saying, “Mary experienced a set of symptoms where your face heats up and turns red, your blood pressure noticeably rises, and you feel a strong desire to be aggressive, whether verbally or physically. You then tend to regret your actions in that state.” It is more efficient to say “Mary was livid with rage.” By convention, the use of the word livid signals that Mary is probably not thinking too clearly at the moment and that the next thing that Mary says or does is probably going to be impulsive and possibly hurtful. 

 Hence, in The Nature of Vocabulary Acquisition, Robert J. Sternberg of Yale University said: 

 “… if one wants a quick and not-too-dirty measure of a person’s psychometrically measured intelligence, and thus has time to give just one brief test of it, vocabulary is [probably] the best predictor of overall score on a psychometric IQ test. (p. 90)” 

 

Here are some examples of questions in vocabulary tests:

As such, one way to estimate one's lexical knowledge by their speech is to pay attention to the efficiency of their communication. The ability to sift through their library of words and use them in the right context to form a sentence relies heavily on IQ. 

An example of having a poor vocabulary is conflating (or, conversely, correctly distinguishing) near-synonyms such as: 

• Envy (discontented longing for someone else's acquisitions) and jealousy (worry another is trying to take what you have, like a partner). 
  
  
• Fewer (used for discrete quantities, anything that can be counted) and less (used for continuous quantities, what cannot be counted). For example, there can be fewer people in a room but not less people. However, there can be less weight in a room, but not fewer.
  
  
• Aggression (a behaviour motivated by the intent to cause harm to another person who wishes to avoid that harm) and violence (a subtype of aggression, a physical behaviour with the intent to kill or permanently injure another person.)
  

Here are other examples of IQ test questions so you can get a better understanding of other things that IQ measures (answers provided at the end of the questions):

1. Which one of the five is least like the other four?

• Dog
• Mouse
• Lion
• Snake
• Elephant

2. Which number should come next in the series 1 - 1 - 2 - 3 - 5 - 8 - 13 ?

• 8
• 13
• 21
• 26
• 31

3. John needs 13 bottles of water from the store. John can only carry 3 at a time. What's the minimum number of trips John needs to make to the store?

• 3
• 4
• 4 1/2
• 5
• 6

4. If all Bloops are Razzies and all Razzies are Lazzies, all Bloops are definitely Lazzies.

• True
• False

5. Choose the word most similar to "Trustworthy":

• Resolute
• Tenacity
• Relevant
• Insolent
• Reliable

6. This sequence of four words, "triangle, glove, clock, bicycle," corresponds to this sequence of numbers "3, 5, 12, 2"

•  True
•  False

7. If Richard looks into a mirror and touches his left ear with his right hand, Richard's image seems to touch its right ear with its left hand. 

•  True
•  False

8. Sixteen hours are to one day as twenty days are to June's length.

•  True
•  False

9. In the English alphabet, there are exactly four letters between the letter "M" and the letter "G."

•  True
•  False

10. Without the aid  of any external tools, read the following mathematical operation, look away, and solve it: 4 + 5.5 * 6

11. What is the name of the ocean that is located between Africa and Australia?

The issue with the above questions is that they rely on the test-taker to speak fluid English and to have a typical Western education. As such, we say it is not culturally fair. A culture-fair IQ test is Raven's Progressive Matrices. For example:

12.

13.

14.

Moreover, visual-spatial processing tests rely relatively on prior knowledge. For instance, in the question below, one must find what shapes can be rotated (but not flipped) to make up the figure on top.

15.

16.

17.

And another example of nonverbal reasoning independent of prior knowledge, particularly with quantitative reasoning (rather than visual-spatial):

18.

19.

Answers

1. Snake
2. 21
3. 5
4. True
5. Reliable
6. True
7. True
8. True
9. False
10. 37
11. Indian
12. Option G
13. Option A
14. Option D
15. Options 1, 4, and 6.
16. Option D
17. Second image from the left
18. Option 2
19. Option 3

Crystallised and Fluid Intelligence

IQ tests for both crystallised and fluid intelligence. In the example questions above, the first set of questions (that aren't culturally fair) rely on some learnt content and hence rely on some crystallised intelligence. However, the second set of questions (the culturally-fair ones), rely entirely on fluid intelligence.

Fluid intelligence is the ability to solve novel problems and crystallised intelligence is regarded as the result, or application, of fluid intelligence. A useful analogy is to think of fluid intelligence as one's adeptness or natural aptitude at writing computer programs (i.e., the capacity to create knowledge) and crystallised intelligence is the computer programs (i.e., the quality of one's knowledge). This is why people's crystallised intelligence never really stops growing (in the exception of brain damage):

Despite fluid intelligence dropping in your late 20s, what you've learnt stays with you; it's just your rate of learning that slows down.

By now you may have realised that the vocabulary tests we talked about earlier are tests of crystallised intelligence. However, if we were to give people new words and test how well they master these new words, that would measure fluid intelligence.

Here is one more example of fluid versus crystallised intelligence. Think of that smart person in high school who can easily solve the following problem without having learnt anything prior:

Mary is twice as old as her sister Rita who is eight years old. How old is Rita when Mary is thirty two years old?

Whereas the studious and conscientious but unintelligent person has to use algebraic strategies they've learnt to solve the problem:

Mary's age = 2 * Rita's Age  = 16

[...]

Thus, if M=32: R=32-8 = 24

Additionally, the second person would struggle to reason through this problem without the assistance of formulas, pen and paper to keep track of the working. 

IQ and Real-World Achievements

Academic Achievement

“The predictive validity of g is most conspicuous in the domain of scholastic performance”

-Some pretentious Wikipedia editor.

In other words, the area that IQ matters the most is in academic performance (unsurprisingly). However, even within the academic world, IQ matters for some subjects more than others. First try to think of the different subjects taught in high school and university and try to rank-order them by how much they rely on IQ, and then see how your guesses compare to the statistics below.

See the summary points from a published meta-analysis:

“Concerning the moderating effect of the subject domains, our analyses showed that the mean corrected correlation between scores of intelligence tests and school grades was highest in the Mathematics and Science subgroup (ρ = .50). 

[...] 

Nevertheless, the mean corrected correlation between intelligence and school grades in Language (ρ = .42) and Social Sciences (ρ = .43) still is rather high, which indicates that cognitive ability is a substantial prerequisite for scholastic success in these subjects.  

[...]  

[There is also] a corrected mean correlation (ρ = .29) between [music\arts and IQ] which is in line with the literature suggesting a relationship between musicality and intelligence (e.g., Schellenberg, 2005) as well as creativity and intelligence (Batey & Furnham, 2006).   

[...]  

Lastly, there is no correlation found between IQ and performance in sports at school."  

[...] 

This finding appears to be rather straightforward since mathematics and science are subjects that deal with content that relies heavily on logic. As logical thinking is the most dominant competence assessed by intelligence tests, persons with higher tests scores should understand the content of these subject domains better and thus have better grades. A second explanation involves the reliability of school grades in these subjects. As answers in written exams in mathematics and science can easily be evaluated as right or wrong there is no margin of judgment [i.e., error] for the teachers when giving the grades. Thus, the reliability of grades in these school subjects should be higher than in the other school subjects where there is clearly a wider margin of judgment, which in turn influences the height of the correlation which can be achieved maximally.  

[...] 

[The above findings] and the finding that the mean corrected validities are lower [in subjects such as language and art] than in the Mathematics and Science subgroup can be explained by the fact that successful participation in [languages and arts] subjects requires learning content (e.g. historical data) by heart. Thus, motivational aspects play a more important role in these subjects than in the Mathematics and Science subgroup where it is predominantly important to understand the content.” 

So it is unsurprising to see results such as these:

(Note: IQ correlates very strongly with SAT scores)

You might have noticed two things from that last table. First, subjects that rely on understanding complex abstractions are at the top. Second, subjects that rely on a wider range of skills have a stronger correlation with IQ. For instance, performance in physics correlates more strongly with IQ than performance in mathematics because physics relies not only on mathematics but also on understanding the scientific method and scientific writing. 

This makes sense when we think back to IQ being the overarching factor responsible for improved performance across domains. Even though mathematics relies heavily on IQ, mathematics also relies on natural talent for, and interest in, quantitative abstractions. To reduce the latter confounding variable (the noise), IQ tests measure all sorts of skills. Hence, a mix of mathematics, reasoning and complex language in physics makes it a better estimator of IQ than mathematics alone.

Average IQ Across Levels of Education

One dataset with the mean for Bachelor's, Master's and PhD/LLD/MD:

• High school certificate 105 (63rd percentile)
• Bachelor’s degree 113 (81st percentile)
• Master’s degree 117 (87th percentile)
• PhD, LLD, MD 128 (97th percentile)

A different source of data with a box plot. But first, learn how a box plot works:

And now for the data:

The jump from Bachelor's to Master's is unsurprising, but the far bigger difference between a Master's and a PhD is surprising to most people. See why that is:

“The focus of master's degrees and doctorate degrees is different. A master's degree is designed to deepen career-oriented knowledge and skills. A doctorate degree is a heavily research-based degree, designed to develop critical research, analytical and writing skills in an effort to fill industry knowledge gaps.”

 

“They’re very different. Getting a Master’s is not all that different from getting a Bachelor’s. The work is at a higher level, obviously, but it’s still mostly classwork. The thesis is like an extended term paper. If you do well as an undergrad, take the same study habits you develop there and apply them to your Master’s studies, and you’ll do fine.” 

 

“Doing the Ph.D. was about learning to think differently. There’s often additional seminar coursework, but that’s about learning / honing critical thinking. If one is going to do solid research, one needs to know how to read the work in the field and to figure out what’s valuable and what’s not. Additionally, if one knows how to properly evaluate research, one is better prepared to design and evaluate their own work.

Finally, there’s the dissertation, which is about learning how to refine a research problem, how to design a course of action to test the hypothesis / hypotheses, and then evaluating the results.

Elements of all of that should be taught even in primary school, but being able to do that independently and well for large problems is what a PhD is training for. For everyone with whom I’ve discussed their PhD process, that required learning to think differently.”

Occupational Achivement

Try to guess the average IQ for different occupations. Graphs below.

Crucial Distinction Between IQ and Personality

In everyday language, people tend to use words such as "intelligent" as umbrella terms, encapsulating a range of different desirable attributes within them. For example, traits like honesty, reliability, industriousness, conscientiousness, sympathy, organised, et cetera. However, these traits have no significant relationship with IQ—they're entirely explained by personality in psychometrics.

Big Five Openness to Experience

A trickier set of personality traits are those under openness to experience because some of them correlate with some aspects of IQ. 

Summarised in the study A Neuropsychological Study of Personality: Trait Openness in Relation to Intelligence, Fluency, and Executive Functioning:

Openness correlates more strongly with verbal/crystallized intelligence (Gc; r=0.44) than with executive functioning (r=0.16) and fluency (r=0.22).

[...]

Further, the partial correlation between Openness and Gc increased from r=0.26 among young adults to r=0.53 among elderly adults. These findings suggest that Openness is more closely associated with the acquisition of broad verbal intellectual skills and knowledge than with executive abilities localized to a specific brain region or neurotransmitter system.

As such, the traits of being inquisitive, intellectual, progressive, et cetera aid in the "search for knowledge" but studies find small correlations with fluid intelligence. However, these traits are most helpful in subject areas like philosophy, linguistics, and some hard sciences, and have no relationship with performance in subjects like law and medicine.

Furthermore, some studies find correlations as high as 0.50 between the personality trait "intellect" and IQ. However, these studies have a poor methodology. See this for yourself by examining the questions they use for intellect from the big five aspect scale:

Positive correlation:

• Am quick to understand things.
• Can handle a lot of information.
• Readily solve complex problems.
• Have a rich vocabulary.
• Think quickly.
• Formulate ideas clearly.

Negative correlation:

• Have difficulty understanding abstract ideas.
• Avoid philosophical discussions.
• Avoid difficult reading material.
• Learn things slowly.

Psychometric researchers argued that this factor showed up in the factor-analyses as self-report for IQ rather than personality. However, IQ tests are far better estimates of one's g-factor than self-reports such as these. In fact, studies have shown that one's perceived intelligence correlate about as much with IQ as they do with narcissistic traits such as boastfulness, grandiosity and low modesty.

Questions that measure personality should not focus on abilities or competence, but only on preferences, values, and behavioural tendencies. For instance, many of the above questions have been rephrased as "I enjoy solving puzzles" or "I tend to engage in philosophical discussions" or "I'm an introspective person" to capture the personality trait openness to experience rather than IQ. 

Another flaw with people estimating their own IQ: 

And when estimating their ability on a logical reasoning test:

Note that the people who score lowest on logical reasoning are far worse at estimating their ability than those that are low IQ, which brings us to another distinction: rationality versus IQ.

Crucial Distinction Between IQ and Rationality

Analytical, critical thinking, logical correlate with but are considered rationality. Can be increased. They are skills similar to how one becomes good at math.

The Savanna-IQ Interaction Hypothesis

Several studies have accumulated evidence that substantiate the Savanna-IQ interaction hypothesis.

Personality traits/behaviours in high IQ people.

“The origin of values and preferences is an unresolved theoretical question in behavioural and social sciences. The Savanna-IQ Interaction Hypothesis, derived from the Savanna Principle and a theory of the evolution of general intelligence, suggests that more intelligent individuals may be more likely to acquire and espouse evolutionarily novel values and preferences (such as liberalism and atheism and, for men, sexual exclusivity) than less intelligent individuals, but that general intelligence may have no effect on the acquisition and espousal of evolutionarily familiar values. Macro-level analyses show that nations with higher average intelligence are more liberal (have greater highest marginal individual tax rate and, as a result, lower income inequality), less religious (a smaller proportion of the population believes in God or considers themselves religious) and more monogamous. The average intelligence of a population appears to be the strongest predictor of its level of liberalism, atheism and monogamy.”

Empirical evidence (low correlations)

I did this research for nothing because turns out the correlations are pretty low :)

Nocturnal activities 

 Kanazawa and Perina (2009) contended, and then verified, that intelligent individuals are more inclined to flourish at night. Specifically, humans evolved to be diurnal--to restrict most of their activities to the day rather than to the night. Many arguments reinforce the proposition that humans, throughout evolution, tend to be active mainly in the day.

Accordingly, the modern trend to undertake some activity in the night, a trend that was facilitated by artificial lighting, demands intelligence. That is, according to the Savanna-IQ interaction hypothesis, general intelligence is needed to complete tasks that diverged from the ubiquitous activities in a previous epoch. General intelligence, therefore, should be correlated with willingness to maintain activity during the night. To assess this possibility, high school students completed a test of verbal intelligence, the Peabody Picture Vocabulary Test. In addition, participants were asked to estimate the time they usually retire to bed on both school days and weekends. Consistent with the Savanna-IQ interaction hypothesis, students who performed well on the test of verbal intelligence also typically retired to bed late (Kanazawa & Perina, 2009).

There is a strong broader body of evidence for the general association between evolutionary novelty and high intelligence. This can be seen in studies of the positive association between high intelligence and liberalism (defined to mean caring about genetically unrelated others), vegetarianism, healthiness and maintaining an exercise regime, nocturnal activity, experimentation with drugs, binge drinking, monogamy, homosexuality and atheism, among others (see Kanazawa, 2012b for review). Kanazawa

(2012b) also notes that IQ does broadly increase as we move away from the Savanna (see also Ash & Gallup, 2007 or Lynn & Vanhanen, 2012)

Classical and other songless music.

Songless (instrumental) music is evolutionarily novel and thus the more intelligent are more inclined to like it. 

"Preference for instrumental music indicates higher intelligence, research finds. People who like ambient music, smooth jazz, film soundtracks, classical music and similar genres without vocals tend to have higher IQs."

"Vuoskoski, Thompson, McIlwain, and Eeerola (2012) found that sad music is often connected to the experience of more complex emotions such as nostalgia, peacefulness, and wonder. The enjoyment of sad music is related to the specific personality traits of openness to experience and empathy (Vuoskoski et al., 2012). Garrido and Schubert (2011) also found that absorption and music empathizing were the best predictors of sad music preference. "

Conversely, upbeat, conventional, popular music with vocals lower IQ.

Nationalism

Nationalists are shooped

Indirectly Estimating IQ

Consider what you know IQ to be now, and the traits that are associated (or not associated) with it. Then use those to do the below estimations.

Examples of what to look for in daily interactions:

• Synthesis of ideas in conversation: 
   - "[Synthesising] involves combining ideas from a range of sources in order to group and present ideas, themes and issues in a logical manner"
   - "Unlike summarising and paraphrasing, which use the ideas of one author at a time, synthesising combines ideas from more than one source and integrates them into your argument."
  
  
• Being articulate:
   - "If you describe someone as articulate, you mean that they are able to express their thoughts and ideas easily and well."
   - "The definition of articulate is someone capable of speaking easily and clearly, and is most often referred to someone who is well-spoken. An example of an articulate person is President Barack Obama."
  
  
• Having a thorough understanding of a wide range of topics (this is literally used in IQ tests). I.e., having a lot of conversation options.
  
  
• Follows and predicts information. A good example would be when watching a movie together. The ability to follow the plot, keep track of the details and hence make predictions is a skill used in IQ tests.
  
  
• Picks up on complex systems or ideas quickly. Like quickly learning a game, how to operate a drone, etca etca !

First, calibrate your intuition by instead of using IQ, using height. Then compare with the stats. You can Google them or ask me :)

Rank in 1,000

Suppose there is a randomly-selected sample of adults from your age group (e.g., 20-30 years old) with 1,000 people in it. Consider that this randomly-selected sample includes all sorts of people—ranging from people in highly gifted programs to those that barely managed to learn how to read and had to drop out of high school. 

Also, consider that someone with average/normal intelligence is at the 50th percentile, so they would score higher than about 500 of the 1,000 people (half of all people). That means they would also score lower than about 500 in 1,000.

If we clinically administered IQ tests to all 1,000 of those people, what rank do you think you (or the person you're estimating) would be at? In other words, how many of the 1,000 people would score higher than them and how many of the 1,000 would score lower than them? Although these two should match, we might intuitively give slightly different numbers due to them being two different frames of reference.

Standing on the normal distribution

Familiarise yourself with the normal distribution. Height is often an intuitive way to begin.

The distribution of the heights of 100 American men:

Visualised with people rank-ordered:

And if included about 100 men and 100 women, there would be two distributions because men are taller than women:

Now being familiar with the normal disbution, suppose that instead of graphing people's heights, we graphed them by IQ. 

Place the person you're estimating somewhere on either of the two distributions below:

Note that each line from the centre represents a change of one standard deviation.

Estimate an IQ score

Here are some classifications for each IQ range so that you can get a feel for what each IQ range is labelled:

Think back to the average IQ of people in the different jobs, educational levels, degrees, et cetera. 

Also, keep in mind that although the average IQ of someone who graduated high school is 105, the average IQ of the population is 100. 

Now simply give a number to the person you're estimating.