Most people are familiar with the little security decals that electronic and other high-value stores use to deter shoplifters. The sticker contains a metallic strip. Unless deactivated by a store cashier, the sticker sets off an alarm when carried past a detector at the store doors.

These security stickers are actually a form of antenna. The sticker detector sends out a weak RF signal between two posts through which shoppers will pass. It looks for a return signal at a specific frequency, which indicates that one of the stickers has entered the field between the posts.

All this theory was obvious to a couple of California Institute of Technology students Dwight Berg and Tom Capellari, who decided to test the system in practice. Naturally, they selected a freshman to (unknowingly) participate in the trials. At preregistration, after the unlucky frosh's picture was taken but before it was laminated onto his I.D. card, Dwight and Tom fixed a couple of active security decals from local stores onto the back of the photo.

The stunt card was then laminated together, hiding the gimmick, and the two conspirators awaited further developments. A couple of months later they caught up with their victim as he was entering one of the stores. He was carrying his wallet above his head. In response to a comment that this was an unusual posture, the frosh replied that something in his wallet, probably his bank card, seemed to set off store alarms. He had been conditioned to carry his wallet above his head after several weeks of setting off the alarms while entering and leaving many of the local stores.

The frosh seemed unimpressed with Dwight and Tom's suggestion that perhaps the local merchants had installed some new type of nerd detection system. Apparently though the comment got the frosh thinking, because on the next occasion when he met Dwight he put him in a headlock until he confessed to his misdeed. Moral: Never annoy a computer programmer.