Intelligence is measured by intelligence quotient (IQ) tests. The average IQ is 100; about two-thirds of people have an IQ between 85 and 115. About 2.5% of people have an IQ above 130, which means they’re in the top 2.5%, that is, among the most intelligent people in the world. People with an IQ below 70 are often considered mentally disabled.
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Calculate the concept of IQ
Intelligence measures are usually thought of as one-dimensional; the average person has an IQ of 100, the standard deviation is 15, and so on. This makes it possible to compare scores to find who is in the top 1% or the bottom 1%, but it also obscures the fact that intelligence is really a collection of different abilities. The most common classification distinguishes three factors: crystallized intelligence (knowledge), fluid intelligence (reasoning), and short-term memory.
Each factor can be measured independently. People’s scores on these three factors correlate somewhat, but not perfectly. For example, a person with good short-term memory might have average crystallized intelligence and below-average fluid intelligence. Or a person who has scored well on tests of crystallized intelligence all their life may suddenly lose their memory, due to Alzheimer’s disease or some other cause.
The three types of intelligence are all important for different things. To do creative work you need both crystallized and fluid abilities, and good short-term memory helps in every kind of work. But none of them is sufficient by itself.
Intelligence is made up of a combination of different factors
Intelligence is the ability to learn from experience, solve problems, and use knowledge to manipulate one’s environment. Many psychologists have attempted to define intelligence in terms of factors that are either innate or acquired through learning. One approach is based on the theory that intelligence is made up of a combination of different factors, such as verbal comprehension, memory, and analytical reasoning. Others believe that intelligence consists of a single general factor (called g) and several other specific abilities that help people acquire knowledge.
Charles Spearman was among the first psychologists to develop a comprehensive theory of intelligence. Spearman proposed that people differ mainly in how much of what he called g they possess. People who score high on tests of general ability also tend to perform well on most mental tests, whereas those who score low tend to do poorly on most tests. In addition to g, Spearman believed that people differ in their specific abilities such as verbal comprehension, perceptual speed, and spatial visualization which he called s factors. However, advocates of alternative theories argue that it is not necessary to invoke specific abilities: For example, Robert Sternberg emphasizes practical intelligence (the ability to adapt effectively to one’s environment) rather than academic or analytic intelligence (the ability to solve problems in a school or laboratory setting).
The Intelligence quotient is a good indicator of intelligence
IQ is not a single number. It’s a whole distribution of numbers, spread out in the familiar bell curve shape. For convenience, IQ scores are usually represented as a single number in the middle of this distribution, called the “mean”. By definition, half the population has an IQ at or below this number, and a half above it.
But even this means turns out not to be very meaningful. The real meaning of an IQ score is its position relative to other people’s scores: if you have an IQ of 100, that means you’re smarter than about 68% of the population. This means that in any given group of people (like a classroom), there will be some with lower IQs than yours and some with higher ones. Often many higher ones, if you’re in a class at Stanford or MIT, almost everyone will be smarter than you are.
In general, IQ isn’t a very good predictor of any one person’s future achievement although it’s true that something like your IQ remains the best predictor we have for how well you’ll do in school.
IQ scores can’t predict your success in life
IQ is not a simple scalar quantity. It’s not just a number. It’s an abstraction that we use to talk about different aspects of intelligence, the way speed is an abstraction we use to talk about how fast someone can run or how fast they can think. There is no single factor called “intelligence” that determines your success in life and is inherited in a simple Mendelian fashion. There are many different mental abilities, each somewhat independent of the others, and each with its own distribution in the population.
Different tests measure different things. Some measure verbal ability, and measure spatial ability; while measuring math ability; some measure short-term memory; while measuring long-term memory; some are speeded and penalize people who are slower thinkers; some are not speeded but still penalize people who have trouble concentrating for long periods on boring tasks (who may nevertheless be quite good at paying attention to interesting tasks).
The average test-taker tends to do best on tests that have a big memory component and a lesser but still significant verbal component. The average test-taker does worse on tests that have big math or spatial component. Tests like this tend to be more g-loaded, meaning they correlate more highly with overall IQ as measured by other factors.
The relationship between intelligence and education
The relationship between intelligence and education is not a trivial one. There are two reasons for this. First, it is believed that education itself has some direct effect on intelligence, that people are more intelligent if they have had more education and less intelligent if they have had less education, apart from whatever intelligence they may have had to begin with. Second, the relationship between intelligence and education has been important in certain recent controversies about educational policy.
The most obvious effect of education on intelligence is that it tends to increase your vocabulary. We do not know whether there are other effects of this kind, but it would seem unlikely that there are not. The longer you go to school, the more words you learn, and there is no reason to think that this would not be accompanied by an increase in general verbal ability as well.
The relationship between IQ scores and educational attainment has been found to be moderate, with high IQs correlating positively with the education level achieved. Those who have high IQs tend to pursue more education than those who have lower ones. Moreover, those who are highly educated tend to have higher IQ scores than those with less education for a variety of social and economic factors.