sciencehabit writes: Social beasts—humans, elephants, chimps, dogs, and cats—seem to enjoy being caressed. Neurobiologists have now taken a step toward pinpointing neural circuitry underlying this pleasant sensation. Using genetically engineered mice, they demonstrated that a specific class of sensory cells in skin reacts to gentle stroking but not to a pinch or a poke. In addition to helping to identify similar cells in people, the findings could "lead to a drug or lotion that might make you feel better," suggests the study's leader.
We warn the reader in advance that the proof presented here depends on a
clever but highly unmotivated trick.
-- Howard Anton, "Elementary Linear Algebra"