The document discusses various theories of intelligence proposed by different psychologists. It describes Charles Spearman's theory of general intelligence (g factor) and Louis Thurstone's theory of primary mental abilities. It also summarizes Howard Gardner's theory of multiple intelligences consisting of nine distinct intelligences. Robert Sternberg proposed successful intelligence involving analytical, practical and creative abilities. The document also discusses theories by David Perkins involving neural, experiential and reflective intelligence. It covers early research on quantifying mental ability by Galton and Binet's development of intelligence tests. It defines concepts like mental age, chronological age and intelligence quotient. The four branches of emotional intelligence - perceiving, using, understanding and managing emotions - are outlined. Gender