The document discusses the phenomenon of the "uncanny valley" where humanoid robots that are close to, but not perfectly human-like, tend to elicit feelings of unease, revulsion or discomfort. It provides examples of robots at different points on the spectrum from industrial robots to highly humanoid robots. It also explores some potential explanations for the uncanny valley effect, including the idea that imperfect human replicas trigger cognitive dissonance by challenging concepts of human uniqueness and identity.