Maslow's Hierarchy of Needs
"Abraham Maslow (1954) attempted to synthesize a large body of research related to human motivation. Prior to Maslow, researchers generally focused separately on such factors as biology, achievement, or power to explain what energizes, directs, and sustains human behavior. Maslow posited a hierarchy of human needs based on two groupings: deficiency needs and growth needs. Within the deficiency needs, each lower need must be met before moving to the next higher level. Once each of these needs has been satisfied, if at some future time a deficiency is detected, the individual will act to remove the deficiency. The first four levels are:
1) Physiological: hunger, thirst, bodily comforts, etc.;
2) Safety/security: out of danger;
3) Belonginess and Love: affiliate with others, be accepted; and (..)"
4) Esteem: to achieve, be competent, gain approval and recognition.