Consider the following scenario: Joe woke up one morning and found he was bitten all over by some sort of mystery bug. The next night, he felt itchy, especially on his torso, near where he'd gotten the other bites. He did not feel the same sensation on his legs, and he knew it must be psychosomatic. He treated his bed for a variety of different bugs, and the bites stopped, but he associated his bed with feelings of itchiness for several weeks. Eventually the response went away, only to suddenly show back up six months later! l