“Unless I Put My Hand into His Side, I Will Not Believe”

Touch seems to enjoy some epistemic advantage over the other senses when it comes to attesting to the reality of external objects. The question is not whether only what appears in tactile experiences is real. It is whether only what appears in tactile experiences feels real to the subject. This chapter first clarifies how the rather vague idea of an epistemic advantage of touch over the other senses should be interpreted. It then defends a “muscular thesis,” to the effect that only the experience of resistance to our motor efforts, as it arises in effortful touch, presents us with the independent existence of some causally empowered object. Finally the chapter considers whether this muscular thesis applies to the perception of our own body.

Global broadcasting of local fractal fluctuations in a bodywide distributed system supports perception via effortful touch

A long history of research has pointed to the importance of fractal fluctuations in physiology, but so far, the physiological evidence of fractal fluctuations has been piecemeal and without clues to bodywide integration. What remains unknown is how fractal fluctuations might interact across the body and how those interactions might support the coordination of goal-directed behaviors. We demonstrate that a complex interplay of fractality in mechanical fluctuations across the body supports a more accurate perception of heaviness and length of occluded handheld objects via effortful touch in blindfolded individuals. For a given participant, the flow of fractal fluctuation through the body indexes the flow of perceptual information used to derive perceptual judgments. These patterns in the waxing and waning of fluctuations across disparate anatomical locations provide novel insights into how the high-dimensional flux of mechanotransduction is compressed into low-dimensional perceptual information specifying properties of hefted occluded objects.