Charles Spearman's Two-Factor Theory of Intelligence
Charles Spearman proposed his two-factor theory of intelligence in 1927. This theory was a significant contribution to the field of psychology and intelligence testing.

Key Points of the Two-Factor Theory:
- Spearman's theory suggested that intelligence is composed of two factors: the general factor (g factor) and specific factors (s factors).
- The g factor represents a person's overall cognitive ability and is responsible for performance on a wide range of cognitive tasks.
- The s factors, on the other hand, are specific abilities that are unique to particular tasks or domains.

Spearman's Research:
- Spearman's theory was based on his research using statistical techniques, particularly factor analysis.
- He found that scores on different cognitive tests tended to be positively correlated, suggesting the presence of a general factor underlying intelligence.
- Spearman also observed that while individuals may excel in specific areas, there was still an underlying general intelligence that influenced overall cognitive performance.

Impact of the Two-Factor Theory:
- Spearman's two-factor theory laid the groundwork for later theories of intelligence, including Cattell's theory of fluid and crystallized intelligence.
- It also influenced the development of intelligence tests, such as the Wechsler Adult Intelligence Scale, which incorporates measures of both general and specific cognitive abilities.
In conclusion, Charles Spearman proposed his two-factor theory of intelligence in 1927, highlighting the presence of a general factor (g factor) and specific factors (s factors) in cognitive abilities.