Clayton Alderfer

Clayton Paul Alderfer (born September 1, 1940 in Sellersville, Pennsylvania) is an American psychologist who further developed Maslow’s hierarchy of needs by categorizing the hierarchy into his ERG theory (Existence, Relatedness and Growth).

The existence group is concerned with providing the basic material existence requirements of humans.

They include the items that Maslow considered to be physiological and safety needs.