In 1878, neurologist George Miller Beard noted a strange trait among the French-Canadian lumberjacks in the Moosehead Lake area of Maine — they reacted strongly when startled:

• “One of the jumpers while sitting in his chair with a knife in his hand was told to throw it, and he threw it quickly, so that it stuck in a beam opposite; at the same time he repeated the order to throw it, with cry or utterance of alarm resembling that of hysteria or epilepsy.”
• “He also threw away his pipe when filling it with tobacco when he was slapped upon the shoulder.”
• “Two jumpers standing near each other were told to strike, and they struck each other very forcibly.”
• “One jumper when standing by a window, was suddenly commanded by a person on the other side of the window, to jump, and he jumped straight up half a foot from the floor, repeating the order.”
• “One of these jumpers came very near cutting his ‘throat’ while shaving on hearing a door slam.”
• “They had been known to strike their fists against a red-hot stove; they had been known to jump into the fire and into water; they could not help striking their best friend, if near them, when ordered.”
• “It was dangerous to startle them in any way when they had an axe or knife in their hand.”

The condition, whatever it was, ran in families, chiefly among men, and the jumpers were otherwise “modest, quiet, retiring, deficient in power of self-assertion and push.” Similar cases have since been observed in Malaysia and Siberia, but no one knows whether the disorder is ultimately neurological or psychological.