After 3 versions of the test (Series A, Series B, and Series C), Morgan and Murray decided on the final set of pictures, Series D, which remains in use today. Murray and Morgan spent the 1930s selecting pictures from illustrative magazines and developing the test. Murray reasoned that by asking people to tell a story about a picture, their defenses to the examiner would be lowered as they would not realize the sensitive personal information they were divulging by creating the story. The rationale behind the technique is that people tend to interpret ambiguous situations in accordance with their own past experiences and current motivations, which may be conscious or unconscious. Murray wanted to use a measure that would reveal information about the whole person but found the contemporary tests of his time lacking in this regard. She reported that when her son was ill, he spent the day making up stories about images in magazines and she asked Murray if pictures could be employed in a clinical setting to explore the underlying dynamics of personality. Anecdotally, the idea for the TAT emerged from a question asked by one of Murray's undergraduate students, Cecilia Roberts. Morgan at the Harvard Clinic at Harvard University. Murray and lay psychoanalyst Christiana D. The TAT was developed during the 1930s by the American psychologist Henry A. Historically, the test has been among the most widely researched, taught, and used of such techniques. Proponents of the technique assert that subjects' responses, in the narratives they make up about ambiguous pictures of people, reveal their underlying motives, concerns, and the way they see the social world. Thematic apperception test (TAT) is a projective psychological test.