According to psychologist Henry Murray (1893-1988), personality is organized based upon a number of needs, motives and environmental forces. Among the needs identified by Murray are those for achievement, intimacy and power. Since Murray first proposed his theory, a number of other psychologists have studied these individual needs. For example, research on the need for achievement has demonstrated that people with a high need to achieve tend to take on greater challenges. Learn more about Murray's theory of psychogenic needs.