Why ‘Gorilla Arm Syndrome’ Rules Out Multitouch Notebook Displays | Gadget Lab | Wired.com: “Gorilla arm” is a term engineers coined about 30 years ago to describe what happens when people try to use these interfaces for an extended period of time. It’s the touchscreen equivalent of carpal-tunnel syndrome. According to the New Hacker’s Dictionary, “the arm begins to feel sore, cramped and oversized — the operator looks like a gorilla while using the touchscreen and feels like one afterwards.”
According to the NHD, the phenomenon is so well-known that it’s become a stock phrase and cautionary tale well beyond touchscreens: “‘Remember the gorilla arm!’ is shorthand for ‘How is this going to fly in real use?’.” You find references to the “gorilla-arm effect” or “gorilla-arm syndrome” again and again in the scholarly literature on UI research and ergonomics, too.