According to German researchers, forcing people to be happy and polite all the time is likely to make them sick. They believe most at risk are air hostesses, call center operators, waiters and other workers in close contact with the public.

    Professor Dicter Zapf, a researcher into human emotions at Frankfurt University, said false friendliness led to depression, stress and a lowering of the immune(免疫) system. This can lead to more serious illness such as high blood pressure and so on.“Every time a person is forced to repress his true feelings, there are negative consequences for his health,”said Professor Dieter Zapf.

    In order to reach these conclusions, for over two years, 4,000 volunteers including shop workers and air hostess, were put in an imaginary call center and abused by customers. Some of the participants were allowed to answer back, while others had to be polite and friendly all the time.

    Those who stood up to clients(顾客) had a rapid heartbeat for a brief period, but for those who had to remain friendly, their heart was still racing long after the client had hung up.

    The conclusion reached by the researchers was that“being friendly against one's will causes nothing but stress”.

    Professor Zapf said, “We are all able to control our emotions, but it becomes difficult to do this over a long period as air hostesses are forced to on long flights.”

    “These people need space away from the passengers where they can be on their own and let their feelings run free. We have to get away from the 'customer is king' attitude and show more respect to those working in the service industries.”