The inversion effect in HRI: Are robots perceived more like humans or objects?

The inversion effect describes a phenomenon in which certain types of images are harder to recognize when they are presented upside down compared to when they are shown upright. Images of human faces and bodies suffer from the inversion effect whereas images of objects do not. The effect may be caused by the configural processing of faces and body postures, which is dependent on the perception of spatial relations between different parts of the stimuli. We investigated if the inversion effect applies to images of robots in the hope of using it as a measurement tool for robot's anthropomorphism. The results suggest that robots, similarly to humans, are subject to the inversion effect. Furthermore, there is a significant, but weak linear relationship between the recognition accuracy and perceived anthropomorphism. The small variance explained by the inversion effect renders this test inferior to the questionnaire based Godspeed Anthropomorphism Scale.