In the early 1900s, Austrian psychotherapist Alfred Adler’s notion of basic mistakes and their role in unpleasant emotions made him one of the earliest therapists to address cognition in psychotherapy. His work inspired American psychologist Albert Ellis to develop rational emotive behaviour therapy (REBT) in the 1950s. This is now considered one of the earliest forms of cognitive psychotherapy. It is based on the idea that a person’s emotional distress arises from their thoughts about an event rather than the actual event itself.