When communist militant Cesare Battisti was arrested after decades on the run, he was employing the oldest trick in the criminal handbook: a disguise. Normally clean-shaven, the Italian fugitive was sporting a fake beard. Prior to his capture, the police had released images that illustrated 20 other possible disguises he might have adopted, from thick-rimmed glasses to a shaved head.

It may sound like a scene straight from a screwball comedy, but research has revealed the surprising effectiveness of appearance-altering ruses as a way to conceal one’s identity. Dr. Rob Jenkins, a psychologist at the University of York, recently carried out a study that distinguished between two types of disguise available: evasion and impersonation. The former’s goal is to no longer look like yourse...