How does a rat build a three-dimensional picture of the world using nothing but hair? Mitra Hartmann unpacks the biomechanics of whisker sensing, the distinction between active touch and passive sensation, and her vision for a tactile paintbrush that could scan objects in 3D.

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Hartmann begins by carefully distinguishing active touch from active somatosensation, drawing on James Gibson's original framework. Active touch requires purposeful exploration, not merely muscle engagement. A rat brushing its whiskers against objects to assess texture is performing active touch; a person grabbing a hot pan with a cloth is not. This distinction matters because it frames the central question of her research: how does an animal transform mechanical energy into a perception of th ...