The students were first asked to provide a written report about their daily activities. Each student was then questioned about these activities, and asked to either lie or tell the truth in their answers.
Interspersed with these questions were “filler” questions on a new topic. One group was always asked to tell the truth to the filler questions, a second group had to lie, and a third group was asked to lie or tell the truth in equal measure.
The researchers found that the frequent liars became more adept at lying. The normal difference in reaction times between telling the truth and lying disappeared.