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Definition of intelligence

Intellectual ability is a complex phenomenon, influenced by factors both environmental and biological. Used in its broadest sense, intelligence is what people use to learn, remember, solve problems and in general deal effectively with the world around them. One survey in the late 1980s asked 25 experts to define intelligence and the researchers received many different definitions some of which are:

general adaptability to new problems in life.
ability to engage in abstract thinking.
capacity for knowledge and knowledge possessed.
the ability to judge, understand and reason.

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Measuring Intelligence

Francis Galton was among the first to measure individual differences in intellectual abilities. Based on quantitative studies of prominent individuals and their family trees, he concluded that intellectual ability is inherited in much the same way as physical traits, and he later published his findings in Hereditary Genius (1869). Eventually, Galton modified his original theories to recognize the effects of education and other environmental factors on mental ability, although he continued to regard heredity as the preeminent influence.

Galton's work was followed in 1905 by that of French psychologist Alfred Binet, who introduced the concept of mental age, which would match chronological age in children of average ability. It would exceed chronological age in bright children and would be below in those of lesser ability. Binet's test was introduced to the United States in a modified form in 1916, and with it the concept of the intelligence quotient (mental age divided by chronological age and multiplied by 100). For example, if a 6-year-old girl scored a mental age of 9, she would be assigned an IQ of 150 ((9/6)x100).

The dominant method of studying intelligence in this century has been the psychometric approach. Researchers using this approach believe that intelligence can be measured through the administration of various forms of IQ tests. These tests give a score that reflects how far the person's performance deviates from the average performance of others who are the same age. Most modern tests arbitrarily define the average score as 100.

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Theories of intelligence

Whatever the nature of the IQ test, many researchers believe that a general statistical factor can be extracted from the results of multiple IQ tests mainly due to the fact that people who perform well on one type of intelligence test tend to do well on others also. Charles Spearman named the general mental ability that carried over from one test to another "g" for general intelligence, and decided that it consisted mainly of the ability to infer relationships based on one's experiences.

In the 1960s American psychologists Raymond Cattell and John Horn applied new methods of factor analysis and concluded there are two kinds of general intelligence: fluid intelligence (gf) and crystallized intelligence (gc). Fluid intelligence represents the biological basis of intelligence. Measures of fluid intelligence, such as speed of reasoning and memory, increase into adulthood and then decline due to the aging process. Crystallized intelligence, on the other hand, is the knowledge and skills obtained through learning and experience. As long as opportunities for learning are available, crystallized intelligence can increase indefinitely during a person's life. For example, vocabulary knowledge is known to increase in college professors throughout their life span.

Another approach is Howard Gardner's theory of multiple intelligences, which replaces the general intelligence factor (g ) with seven different types of intelligence: linguistic; logical-mathematical; spatial; interpersonal (ability to deal with other people); intrapersonal (insight into oneself); musical; and bodily-kinesthetic (athletic ability). According to Gardner, each of these areas of competence includes a separate set of problem-solving skills that can be mobilized by various symbolic systems. Every person has all the different types of intelligence, although some may be developed far more fully than others. (The most dramatic example of this is found in savants, mentally retarded people with exceptional abilities in a few highly specialized areas, usually involving calculations.)

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Demographic comparison of IQ scores

Thousands of people have taken this test and their test scores reveal the following interesting facts.

The European cities which scored the highest are: Amsterdam (Holland), Hamburg (Germany).
Males scored marginally higher than females by 1 point.
Left handed people scored higher than right handed people by 2 points.
Aquarians came top of the astrological chart and scorpions last.
Smokers scored higher than non-smokers by two points.
Blue-eyed people marginally beat the brown-eyes by 1points.

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Some famous IQ's

Leonardo da Vinci Artist, Inventor 220 IQ
Voltaire Writer 190 IQ
Garry Kasparov Chess grandmaster 190 IQ
Galileo Galilei Physicist/Astronomer 185 IQ
Descartes Philosopher/Mathematician 180 IQ
Immanuel Kant Philosopher 175 IQ
Plato Philosopher 170 IQ
Charles Darwin Naturalist 165 IQ
Wolfgang Amadeus Mozart Composer 165 IQ
Albert Einstein Physicist 160 IQ

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Interesting facts about your brain and intelligence

Your brain has about 100 billion neurons. A typical brain cell has from 1,000 to 10,000 connections to other brain cells.
Studies have shown that children who are breast fed display IQ's up to 10 points higher by the age of three.
The right side of your brain controls the left side of your body, and the left side of your brain controls the right side of your body.
Your brain weight accounts for about 2 percent of your body weight. But your brain uses 20 percent of your body's oxygen supply and 20 to 30 percent of your body's energy.
When you are born, your brain weighs about a pound. But by age 6, it weighs three pounds. What happens? Learning to stand, talk, and walk creates a web of connections in your head—two pounds worth!
Your brain is full of nerve cells, but it has no pain receptors. Doctors can operate on your brain while you're awake and you won't feel a thing.
In 1984 the political scientist James Flynn reported that Americans had gained about 13.8 IQ points in 46 years. If people taking an IQ test today were scored in the same way as people 50 years ago then 90% of them would be classified in the genius level.
A message for action travels from your brain to your muscles as fast as 250 miles per hour.

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