Motivation is defined as the process that initiates, guides, and maintains goal-oriented behaviors. Psychologists have divided motives into three types: biological motives, which are physiological needs for survival; social motives, such as achievement, aggression, and curiosity; and personal motives like habits, life goals, attitudes, and aspirations. Popular theories of motivation discussed include Hertzberg's two-factor theory, Maslow's hierarchy of needs, the Hawthorne effect, expectancy theory, and the three-dimensional theory of attribution.