It might be a brainwave, but what on earth does it mean?

This morning, I had a remarkable experience: I strolled into a delicatessen and bought some delicious Stilton. What made the shopping trip unusual was that I was wearing a brain scanner while I did it.

My costume consisted of an electroencephalograph (EEG) cap, which looks like a polka-dot shower cap with wires plugged into it; a pair of wrap-around glasses with a tiny video camera attached; a clothes peg on one finger to measure my heart rate; two other finger monitors that functioned like a lie-detector; a thermometer patch on a fourth finger; and a satchel to hold a computer gathering the data.

Most of these devices, or their equivalent, can be hidden under clothes or baseball caps so that the wearer looks as if they are sporting only shades and an iPod, but in my case the boffins hadn’t bothered, and so I entered the deli looking like an extra from a 1970s episode of Doctor Who.

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Tim Harford’s blog

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Tim, also known as the Undercover Economist, writes about the economics of everyday life.