The Rorschach Test is a psychological test in which a person is asked to interpret a series of inkblots. The test was developed by Swiss psychiatrist Hermann Rorschach in 1921 and is used to assess a person's personality characteristics and emotional functioning. The term 'Rorschach Test Mark' refers to the inkblot images used in the test. The four-letter solution to this crossword clue is 'BLOT'.