Humanness beliefs about behavior: an index and comparative human-nonhuman behavior judgments.

Social psychological research suggests that two distinct dimensions describe lay conceptions of humanness: a species-typical sense (i.e., human nature) and a species-unique sense (i.e., human uniqueness). Although these two senses of humanness have been discerned among psychological traits and states, there has been no systematic research into lay beliefs about the humanness of human behaviors. Using a range of 60 prosocial, nonsocial, and antisocial behaviors, it was demonstrated that people discriminate between species-typical and species-unique behaviors and that the capacity to perform species-unique behaviors distinguishes humans from animals, whereas the capacity to perform species-typical behaviors distinguishes humans from robots. Behaviors that exemplify the two senses of humanness are identified, and data representing rankings, raw scores, and z-scores in two indices of species typicality and species uniqueness are provided. Taken together, these findings expand our understanding of lay conceptions of humanness and provide researchers of humanness with a wider range of validated stimuli to probe the boundaries of humanity.