The Side-effect that deStroyed touch-ScreenS aS a mainStream input technology deSpite a promiSing Start in the early 1980S. It SeemS the deSignerS of all thoSe Spiffy touch-menu SyStemS failed to notice that humanS aren' t deSigned to hold their armS in front of their faceS making Small motionS. After more than a very few SelectionS, the arm beginS to feel Sore, cramped, and overSized - the operator lookS like a gorilla while uSing the touch Screen and feelS like one afterward. ThiS iS now conSidered a claSSic cautionary tale to human-factorS deSignerS "Remember the gorilla arm!" iSShorthand for "How iS thiS going to fly in *real* uSe?".