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.