Bike thefts have been significantly reduced simply by putting pictures of staring eyes above cycle racks, researchers say.
The two-year experiment at Newcastle University was mooted by a security manager at the campus who had seen similar studies suggest that people behave better when they feel they are being watched.
Academics found bike racks which had eyes placed above them experienced 62% fewer thefts compared with the previous year, while those without eyes saw thefts increase by 63%.
The crime-fighting idea is now being trialled by British Transport Police (BTP), with train Company C2C, on a route between London's Fenchurch Street station and Southend in Essex.
Professor Melissa Bateson and Professor Daniel Nettle, of the Centre for Behaviour and Evolution, and Ken Nott, of Newcastle University's security team, talk about their findings in the journal PLoS ONE.
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 eye signs in three locations, leaving the rest of the racks without signs.
They monitored all the sites for a year to measure the impact on the level of crime, and noticed a major drop for racks with eyes but an increase at those without.
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.