Haptic Processing of the Location of a Known Property: Does Knowing What You've Touched Tell You Where It Is?

The relationship between knowing where a haptic property is located and knowing what it is was investigated using a haptic-search paradigm. Across trials, from one to six stimuli were presented simultaneously to varying combinations of the middle three fingertips of both hands. Participants reported the presence/absence of a target or its location for four perceptual dimensions: rough/smooth, edge/no edge, relative position (right/left), and relative orientation (right/left). Reaction time data were plotted as a function of set size. The slope data indicated no difference in processing load for location as compared to identity processing. However, the intercept data did reveal a cost associated with processing location information. Location information was not obtained for "free" when identity was processed. The data also supported a critical distinction between material and edge dimensions versus geometric dimensions, as the size of the cost associated with processing location was larger for spatial than for intensive stimuli.