the false perception that one has been tapped in the middle of the forearm after being tapped rapidly at the wrist and then the elbow: The taps seem to move along the forearm’s length much like a hopping rabbit. This illusion is consistently evoked as long as the tapping span does not cross the midline of the body. Slight variations in the timing of taps on the skin can produce wide fluctuations in the taps’ perceived locations, and evidence from functional magnetic resonance imaging has revealed that the phantom sensations are associated with activity in the primary somatosensory area, the same brain region initially activated by real tactile sensations. See also saltation. [first described in 1972 by U.S. psychologists Frank Arthur Geldard (1904–1984) and Carl Edwin Sherrick (1924–2005)]