1904 — Oskar Pfungst began his examination of “Clever Hans,” the horse supposedly endowed with human reasoning, reading, and mathematical abilities. Pfungst found that the horse’s behavior was attributable to subtle cues from human observers. The case is often cited in discussions of experimenter expectancy effects.

1973 — The island nation of Grenada issued postage stamps honoring Sigmund Freud and Carl Jung. Freud was featured on a 3-cent stamp, Jung on a 35-cent stamp.

1986 — The APA signed the first licensing agreement for PsycLIT with Indiana University at Bloomington.

Text adapted from: History

Picture credit: 1, 2, 3