These two were not creators of art, but were two of the most successful in the field of Psychology, true interpreters of human behavior and personality.
It's impossible to actually quantify their influence in society and the arts, but you need only to grasp a bit of what their theories were all about to realize their influence has been massive.
"Sigmund Freud (German pronunciation: [ˈziːkmʊnt ˈfʁɔʏt]; born Sigismund Schlomo Freud; 6 May 1856 – 23 September 1939) was an Austrian neurologist who became known as the founding father of psychoanalysis."
Freud developed therapeutic techniques such as the use of free association (in which patients report their thoughts without reservation and in whichever order they spontaneously occur) and discovered transference (the process in which patients displace on to their analysts feelings derived from the sexual experiences and fantasies of their childhood), establishing its central role in the analytic process. Freud’s analysis of his own and his patients dreams as wish-fulfilments provided him with models for the clinical analysis of symptom formation and the mechanisms of repression as well as for further elaboration of his theory of the unconscious as an agency disruptive of conscious states of mind. Freud postulated the existence of libido, an energy with which mental process and structures are invested and which generates erotic attachments, and a death drive, the source of repetition, hate, aggression and guilt. In his later work Freud drew on psychoanalytic theory to develop a wide-ranging interpretation and critique of religion and culture."
"Abraham Harold Maslow (April 1, 1908 – June 8, 1970) was an American psychologist who was best known for creating Maslow's hierarchy of needs, a theory of psychological health predicated on fulfilling innate human needs in priority, culminating in self-actualization. Maslow was a psychology professor at Brandeis University, Brooklyn College, New School for Social Research and Columbia University. He stressed the importance of focusing on the positive qualities in people, as opposed to treating them as a "bag of symptoms."
Maslow's hierarchy of needs
"Humanistic psychologists believe that every person has a strong desire to realize his or her full potential, to reach a level of "self-actualization". The main point of that new movement, that reached its peak in 1960s, was to emphasize the positive potential of human beings. Maslow positioned his work as a vital complement to that of Freud"
"It is as if Freud supplied us the sick half of psychology and we must now fill it out with the healthy half."
"To prove that humans are not simply blindly reacting to situations, but trying to accomplish something greater, Maslow studied mentally healthy individuals instead of people with serious psychological issues. He focused on self-actualising people. Self-actualizing people indicate a coherent personality syndrome and represent optimal psychological health and functioning."
"This informed his theory that a person enjoys "peak experiences", high points in life when the individual is in harmony with himself and his surroundings. In Maslow's view, self-actualized people can have many peak experiences throughout a day while others have those experiences less frequently."
"Maslow based his theory partially on his own assumptions about human potential and partially on his case studies of historical figures whom he believed to be self actualized, including Albert Einstein and Henry David Thoreau. Consequently, Maslow argued, the way in which essential needs are fulfilled is just as important as the needs themselves. Together, these define the human experience. To the extent a person finds cooperative social fulfillment, he establishes meaningful relationships with other people and the larger world. In other words, he establishes meaningful connections to an external reality—an essential component of self-actualization. In contrast, to the extent that vital needs find selfish and competitive fulfillment, a person acquires hostile emotions and limited external relationships—his awareness remains internal and limited."~ César ~