Originally coined in 1970 by the eminent Japanese roboticist Masahiro Mori, bukimi no tani refers to a psychological phenomenon in which human emotional responses to artificial figures—such as robots—become increasingly negative as those figures approach human likeness, but fall short of perfect realism.

As the anthropomorphic features of these creations become more refined, subtle imperfections in their appearance or behavior can evoke feelings of unease or revulsion. This discomfort typically subsides only when the likeness achieves a level of realism sufficient to be perceived as genuinely human, rather than a flawed approximation.

bukimi no tani loosely translates to English as the creepy or “uncanny valley.”