Passive human touch cannot recognize the shape of a pattern imprinted on the fingertip

While tactile spatial pattern recognition has been suggested to be qualitatively similar to visual recognition, our study challenges this notion, particularly under passive touch. Previous electrophysiological and behavioral research suggested that the tactile system can process complex spatial patterns in the same way as the visual system and can be modeled as a low-pass version of visual spatial perception. However, we found that when using energy-matched simple patterns, participants were highly dependent on local skin deformation and largely ineffective at distinguishing basic shape features, such as a closed triangle vs. an open arrow, or to discern the similarity of rotated versions of the same shape, regardless of whether they were presented as vibrotactile patterns or braille patterns. This study provides compelling evidence that tactile representation of spatial patterns differs not only in resolution but also in how the brain processes shape features compared to visual representation in standard passive viewing.