Honesty is the best policy, as the English saying goes. Unfortunately, honesty often deser

ts us when no one is watching, British psychologists reported last week.

Researchers at UK's Newcastle University set up an experiment in their psychology department's coffee room. They set a kettle, with tea, coffee and milk on the counter and hung up a sign listing the prices for drinks. People helping themselves to a cup of drink were supposed to put a few cents in the box nearby. The scientists hung a poster above the money box, and it changed each week between images of gazing eyes and pictures of flowers. The researchers found that staff paid 2.76 times more for their drinks when the image of the eyes was hung. "Frankly we were shocked by the size of the effect," said Gilbert Roberts, one of the researchers.

Eyes are known to be a powerful perceptual (感官的) signal for humans. "Even though the eyes were not real, they still seemed to make people behave more honestly," said Melissa Bateson, a behavioral biologist and leader of the study.

Researchers believe the effect sheds light on our evolutionary past. It may arise from behavioral features that developed when early humans formed social groups to strengthen their chances of survival For social groups to work, individuals had to co-operate, rather than act selfishly. "There's an argument that if nobody is watching us, it is in our interests to behave selfishly. But when we're being watched we should behave better. So people see us as co-operative and behave the same way towards us," Bateson said.

The new finding indicates that people have a striking response to eyes. That might be because eyes and faces send a strong biological signal we have evolved to respond to. The finding could be put to practical use, too. For example, images of eyes could increase ticket sales on public transport and improve supervision systems to prevent antisocial behavior.

The experiment conducted in Newcastle University shows that ______.

A．people enjoy free drinks more than paid ones

B．most people are dishonest if nobody is watching

C．people like pictures of flowers more than pictures of eyes

D．people are more honest when watched by pictures of eyes