Evaluating the replicability of the uncanny valley effect

The uncanny valley (UV) effect refers to an eerie feeling of unfamiliarity people get while observing or interacting with robots that resemble humans almost but not quite perfectly. The effect is not well understood, and it is also unclear how well results from previous research on the UV can be replicated. In six studies, both in the laboratory and online (N = 1343), we attempted to replicate the UV effect with various stimuli used in previous research. In Studies 1 and 2 we failed to replicate the UV effect with CGI stimuli created using the so-called morphing technique (a robot image morphed into a human image, resulting in a supposedly creepy robot-human image). In Studies 3a and 3b we found a prominent UV effect using pre-evaluated, non-morphed and photorealistic robot pictures. Finally, in exploratory Studies 4a and 4b we found the UV effect using morphed and photorealistic human and robot pictures. Our results suggest that the UV effect is more robust when elicited by pre-validated or prima facie uncanny robot pictures than by non-photorealistic images generated using the morphing technique. We argue that photorealistic pictures are more suitable than less realistic CGI pictures as stimuli for research attempting to elicit the UV effect – however, our results do not invalidate any previous research on the UV effect using morphing techniques, but point to their domain of applicability and context sensitivity.