Which psychologist conducted one of the earliest studies examining the effectiveness of psychotherapy? fritz perls hans eysenck robert sternberg raymond cattell?

The correct answer is Hans Eysenck. He published in 1952 a paper in which refer the absence of treatment was the same or even better than the psychoanalytic psychotherapy. He directed his efforts towards therapies based on the cognitive behavioral theory

Explanation:

Fritz Pearls developed the Gestalt theory.

Robert Stemberg dedicated his career to the analysis of intelligence, creativity, love, hate and wisdom.

Raymond Cattell developed a theory about intelligence and personality.