While intelligence is one of the most talked about subjects within psychology, there is no standard definition of what exactly constitutes ‘intelligence.’ Some researchers have suggested that intelligence is a single, general ability, while other believe that intelligence encompasses a range of aptitudes, skills and talents.
The following are some of the major theories of intelligence that have emerged during the last 100 years.
Charles Spearman - General Intelligence:
British psychologist Charles Spearman (1863-1945) described a concept he referred to as general intelligence, or the g factor. After using a technique known as factor analysis to to examine a number of mental aptitude tests, Spearman concluded that scores on these tests were remarkably similar. People who performed well on one cognitive test tended to perform well on other tests, while those who scored badly on one test tended to score badly on others. He concluded that intelligence is general cognitive ability that could be measured and numerically expressed.
Louis L. Thurstone - Primary Mental Abilities: