The Mariko Aoki phenomenon (青木まりこ現象, Aoki Mariko genshō) is a Japanese expression referring to a sudden urge to defecate that is felt upon entering bookstores. The phenomenon is named after Mariko Aoki, a woman who described the effect in a magazine article published in 1985. According to Japanese social psychologist Shozo Shibuya, the specific causes that trigger a defecation urge in bookstores are not yet clearly understood (as of 2014). There are also some who are skeptical about whether such a peculiar phenomenon really exists at all, and it is sometimes discussed as one type of urban myth.