People are better behaved when they have a sense of "Big Brother" watching them, research has shown.
Psychologists found that cafe diners were less likely to leave tables untidy when surrounded by posters of staring human faces. When pictures of flowers decorated the walls, more empty plates and litter were left.
The same researchers from the University of Newcastle previously found that images of eyes prompted contributions to an honesty box in a tea room.
Study leader Dr Melissa Bateson said: "We think that the images of eyes work by making people feel watched. We behave better when we feel we are being observed."