Abraham Maslow's hierarchy of needs is one of the best-known theories of motivation. Maslow's theory states that our actions are motivated by certain physiological and psychological needs that progress from basic to complex.

There are 5 levels of needs in Maslow’s hierarchy not counting the expanded hierarchy.

While some of the existing schools of thought at the time—such as psychoanalysis and behaviorism—tended to focus on problematic behaviors, Maslow, a Humanist, was more interested in learning about what makes people happy and what they do to achieve that aim.

In 1970, Maslow built upon his original hierarchy to include three additional needs at the top of his pyramid, for a total of eight:

• Cognitive needs. This centers on knowledge. People generally want to learn and know things about their world and their places in it.
• Aesthetic needs. This addresses the appreciation of beauty and form. People might fulfill this need through enjoying or creating music, art, literature, and other creative expressions.
• Transcendence needs. Maslow believed that humans are driven to look beyond the physical self in search of meaning. Helping others, practicing spirituality, and connecting with nature are a few ways we might meet this need.

• Needs don't follow a hierarchy: While some research has shown support for Maslow's theories, most of the research has not been able to substantiate the idea of a needs hierarchy. Wahba and Bridwell (researchers from Baruch College) reported that there was little evidence for Maslow's ranking of these needs and even less evidence that these needs are in a hierarchical order.5
• The theory is difficult to test: Other critics of Maslow's theory note that his definition of self-actualization is difficult to test scientifically.6 His research on self-actualization was also based on a very limited sample of individuals, including people he knew as well as biographies of famous individuals who Maslow believed to be self-actualized.

Abraham Maslow first introduced the concept of a hierarchy of needs in his 1943 paper, titled "A Theory of Human Motivation," and again in his subsequent book, "Motivation and Personality." This hierarchy suggests that people are motivated to fulfill basic needs before moving on to other, more advanced needs.