A form of psychotherapy aimed at modifying people's beliefs, expectancies, assumptions, and styles of thinking, based on the assumption that psychological problems often stem from erroneous patterns of thinking and distorted perceptions of reality (such as overgeneralizations of the type, People are always letting me down) that can be identified and corrected. It has been applied especially to the treatment of depression. The first widely used form of cognitive therapy, not labelled as such, was rational emotive therapy (RET), and the most influential proponent of a later and more complex form of cognitive therapy was the US psychiatrist Aaron (Temkin) Beck (born 1921). Beck was the first to suggest in his book Depression: Clinical, Experimental, and Theoretical Aspects (1967) that depression-prone people tend to have negative self-schemas revolving around assumptions of inadequacy, failure, loss, and worthlessness; Beck assumed that these beliefs are unrealistic and biased, but research into depressive realism suggests the opposite. See also cognitive behaviour modification, cognitive restructuring, depressive realism.