Birthday-Number Effect

First identified by psychologists Shinobu Kitayama and Karasawa in a 1997 study of Japanese participants, demonstrating that individuals unconsciously assign higher preference ratings to birthday-related digits. The effect was extended to Western contexts by Pelham, Mirenberg, and Jones in 2002 as part of implicit egotism theory, which proposes that people have an unconscious preference for things they associate with themselves. Research has found people disproportionately live in towns whose names contain their birthday numbers.