What psychologist proposed that motivated by five unmet needs?

Maslow's hierarchy of need theory is a psychological theory proposed by Abraham Maslow in his 1943 paper "A Theory of Human Motivation" and his subsequent book Motivation and Personality. Maslow's hierarchy of needs is often portrayed as a pyramid consisting of five levels: physiological, safety, love and belonging, esteem, and self-actualization. The theory suggests that the most basic level of needs must be met before the next level can be addressed.