*Raymond Cattell* Raymond Cattell was a British-American psychologist known for his work on personality, intelligence, and motivation. Key Contributions 1. *16 Personality Factor (16PF) Model*: Cattell developed a personality assessment tool that measures 16 personality factors. 2. *Fluid and Crystallized Intelligence*: Cattell proposed a theory of intelligence that distinguishes between fluid and crystallized intelligence. Fluid and Crystallized Intelligence 1. *Fluid Intelligence*: The ability to reason, think abstractly, and solve problems in novel situations. 2. *Crystallized Intelligence*: The ability to use learned knowledge and experience to solve problems. Applications 1. *Personality Assessment*: Cattell's 16PF model is widely used in personality assessment and research. 2. *Intelligence Research*: Cattell's theory of fluid and crystallized intelligence has influenced research on human intelligence.