Bike thefts have been cut sharply at a university just by placing a poster of watchful eyes above the cycle racks, according to researchers.
The two-year experiment at Newcastle University was suggested by a security manager at the campus who had seen similar studies indicating that people behave better when they feel they are being watched.
Academics found that bike racks where the poster was present had 62% fewer thefts than the previous year, while those without the poster saw thefts rise by 63%.
For the first year, the team monitored the level of bike thefts from all racks across campus for a control figure.
They then placed the posters in three locations, leaving the rest of the racks without signs. Crime levels were monitored at all the sites for a year.
Professor Melissa Bateson and Professor Daniel Nettle, of the Centre for Behaviour and Evolution, and Ken Nott, of Newcastle University's security team, were behind the study.
"We don't know exactly what is happening here but this just adds to the growing evidence that images of eyes can have a big impact on behaviour," said Professor Nettle in the journal PLoS ONE .
"We think that the presence of eye images can encourage co-operative behaviour. One strong possibility is that the images of eyes work by making people feel watched.
"We care what other people think about us, and as a result we behave better when we feel we are being observed."
Mr Nott said: "I had followed previous work done by this team and thought it might be able to make a difference to levels of crime, so I decided to suggest this experiment.
"The results were clear and we have now put these pictures up across all the bike racks on the campus."
A 2006 study found that staring eyes made people pay almost three times as much into a tea-room honesty box.
And research in 2010 showed that people using a canteen were more likely to clear away their tray after a meal when there were eyes watching them.
The crime-fighting idea is now being tried by British Transport Police and train company C2C on a route between London's Fenchurch Street station and Southend in Essex.