Hermann Rorschach, vice president of the Swiss Psychoanalytic Society, designed his 10 inkblots to help diagnose schizophrenia, then died of a ruptured appendix in 1922 at 37, believing his work had failed. This episode traces how he hand drew hundreds of designs, tested them on 300 mental patients and 100 controls, and chose near perfect bilateral symmetry because subjects rejected asymmetrical figures. When his 1921 book Psychodiagnostik went to press, the printer laid down uneven ink, adding shading he embraced as a richer tool. The book barely sold.

After his death, other psychologists used the test on everyone, and in the 1960s John E. Exner built the Comprehensive System, coding location, white space and determinants such as shading. The episode then covers the backlash: Loren and Jean Chapman at the University of Wisconsin showed that accepted clinical signs used to label homosexuality, then classified as a pathology, had no predictive value, an example of illusory correlation. Cultural differences in responses and a 2009 Wikipedia fight over Dr. James Heilman posting all 10 plates followed.

• Leonardo da Vinci’s stains and the Victorian parlor game Gobolinks
• Why the examiner sits beside and slightly behind the patient
• Card IV, the so-called father card, and the chaotic colors of Card X
• French subjects seeing chameleons and Scandinavians seeing Christmas elves
• Heilman’s eye chart argument and the plates’ public domain status