Similar mechanisms underlie curvature comparison by static and dynamic touch

In four experiments, we tested whether haptic comparison of curvature rangi ng from -4/m to +4/m is qualitatively the same for static and for dynamic t ouch. Zn Experiments 1 and 3, we tested whether static and dynamic curvatur e discrimination are based on height differences, attitude (slope) differen ces, curvature differences, or a combination of these geometrical variables . It was found that both static and dynamic haptic curvature discrimination are based on attitude differences. In Experiments 2 and 4, we tested wheth er this mechanism leads to errors in the comparison of stimuli with differe nt lengths for static and dynamic touch, respectively. If the judgements ar e based on attitude differences, subjects will make systematic errors in th ese comparisons. In both experiments, pre found that subjects compared the curvatures of strips of the same length veridically, whereas they made syst ematic errors if they were required to compare the curvatures of strips of different, lengths. Longer stimuli were judged to be more curved than short er stimuli with the same curvature. We conclude that similar mechanisms und erlie static and dynamic haptic curvature comparison. Moreover, additional data comparison showed that static and dynamic curvature comparison is not only qualitatively,but also quantitatively similar.