Existence needs encompass Maslow's physiological and safety needs. Relatedness needs are similar to Maslow's social needs. Growth needs are comparable to Maslow's esteem and self-actualization needs. Growth needs encompass all the needs which involve a person making creative or productive effects on others and the environment.
There are several differences between Maslow's and Alderfer's theories.
First, ERG theory proposes three needs instead of five.
Second, these three needs are organized on a concreteness continuum rather than a hierarchy. Existence needs are the most concrete because they involve objects such as food, water, and shelter. Relatedness needs are next because they involve social relationships. Growth needs are the most abstract because they do not involve physical aspects.
Third, ERG theory is more sophisticated in that needs do not have to operate in a strict, hierarchical fashion (Alderfer, 1969). Recall that Maslow's idea of fulfillment progression went only one way up the hierarchy, but ERG theory allows for a back and forth movement from one need category to another. Alderfer proposed the idea of frustration-regression: when needs are not satisfied, people may regress back to a more concrete need. For example, if an employee's growth needs are unfulfilled at work because he or she is in a dead-end position with no opportunities for advancement, he or she may regress back to relatedness needs and try to gain satisfaction from social interactions with co-workers. If relatedness needs are blocked, then an employee may regress to existence needs and seek refuge in food, alcohol, and drugs to satisfy needs.
There are two exceptions to frustration-regression:
First, failure to fulfill existence needs leads to greater existence needs. For example, if you need food and cannot get any, you develop an even greater need for food.
Second, fulfillment of growth needs leads to greater growth needs. If you are an aspiring writer and write a good book, your need to further your development will increase, similar to Maslow's notion of self-actualization where reaching the pinnacle of the pyramid results in striving even higher.