Conceptual distortions of hand structure are resistant to changes in stimulus information

Hands are commonly held up as an exemplar of well-known, familiar objects. However, conceptual knowledge of the hand has been found to show highly stereotyped distortions. Specifically, people judge their knuckles as farther forward in the hand than they actually are. The cause of this distal bias remains unclear. In Experiment 1, we tested whether both visual and tactile information contribute to the distortion. Participants judged the location of their knuckles by pointing to the location on their palm directly opposite each knuckle with: 1) a metal baton (using vision and touch) 2) a metal baton while blindfolded (using touch), 3) a laser pointer (using vision). In Experiment 2, we investigated whether judgments are influenced by visual landmarks such as the creases at the base of each finger on the palm. Participants localized their knuckles on either a photograph or a silhouette of their hand. In both experiments, clear distortions were found across conditions, of generally similar magnitude. These results show that distal bias is resistant to changes in the stimulus information and does not rely on any specific stimulus cue or single sensory modality, suggesting that such mislocalisations reflect a conceptual misrepresentation of hand structure.