In the 1950s and 1960s, American psychiatrist Aaron T. Beck noticed that his clients had internal dialogues going on in their minds during analytical sessions. He discovered that the clients appeared to almost be talking to themselves, but they only shared a small part of this kind of thinking with him. For example, a person might have thought to themselves, “The therapist is being very quiet today; I wonder if he’s mad at me?” and then began to feel anxious as a result.