
The birthday-number effect is the unconscious tendency of people to prefer the numbers in the date of their birthday over other numbers. First reported in 1997 by Japanese psychologists Shinobu Kitayama and Mayumi Karasawa, the birthday-number effect has been shown to hold across age and gender. The effect is most prominent for numbers over 12. Birth dates are unconsciously associated with the self, and most people like themselves; this has been...