From How Stuff Works:
The term IQ, or Intelligence Quotient, generally describes a score on a test that rates the subject's cognitive ability as compared to the general population. IQ tests use a standardized scale with 100 as the median score. On most tests, a score between 90 and 110, or the median plus or minus 10, indicates average intelligence. A score above 130 indicates exceptional intelligence and a score below 70 may indicate mental retardation. Like their predecessors, modern tests do take in to account the age of a child when determining an IQ score. Children are graded relative to the population at their developmental level. What is this cognitive ability being measured? Simply put, IQ tests are designed to measure your general ability to solve problems and understand concepts. This includes reasoning ability, problem-solving ability, ability to perceive relationships between things and ability to store and retrieve information. IQ tests measure this general intellectual ability in a number of different ways. They may test:
- spatial ability: the ability to visualize manipulation of shapes
- mathematical ability: the ability to solve problems and use logic
- language ability: This could include the ability to complete sentences or recognize words when letters have been rearranged or removed.
- memory ability: the ability to recall things presented either visually or aurally
…Because IQ tests measure your ability to understand ideas and not the quantity of your knowledge, learning new information does not automatically increase your IQ. Learning may exercise your mind, however, which could help you to develop greater cognitive skills, but scientists do not fully understand this relationship. The connection between learning and mental ability is still largely unknown, as are the workings of the brain and the nature of intellectual ability. Intellectual ability does seem to depend more on genetic factors than on environmental factors, but most experts agree that environment plays some significant role in its development.
But can you increase your IQ score?