Touch Impulses

Touch is a much more complicated sense than one might think. Humans have an array of organs that allow them to sense pressure, sheer forces, temperature and vibrations with remarkable precision. (And German researchers have shown that raccoons have evolved the animal world’s most sophisticated brain functions to process touch impulses in the dark.)

Research suggests that our sense of touch is actually several orders of magnitude finer than previously believed. Last fall, for example, Swedish scientists reported in the journal Nature that dynamic human touch — for example, when a finger slides across a surface — could distinguish ridges no higher than 13 nanometers, or about 0.0000005 of an inch.

That is the scale of individual molecules. Or as Mark Rutland, a professor of surface chemistry at the KTH Royal Institute of Technology in Sweden, put it, if your finger were as big as the earth, it could feel the difference between a car and a house. Physiologists have shown that the interaction between a finger and a surface is detected by organs called mechanoreceptors, which are embedded at different depths in the skin. Some are sensitive to changes in an object’s size or shape and others to vibrations.