Silence Please If there is one group of workers across the Western world who will be glad that Christmas is over, that group is shop workers. It is not that they like to complain. They realize that they are going to be rushed off their feet at Christmas. They know that their employers need happy customers to make their profits that pay their wages. But there is one thing about working in a shop over Christmas that is too bad to tolerate. That thing is music. These days, all shops and many offices have what is known as 'Piped music' or 'muzak' playing for all the hours that they are open. Muzak has an odd history. During the 1940s, music was played to cows as part of a scientific experiment. It was found that cows which listened to simple, happy music produced more milk. Perhaps workers and customers who listened to simple, happy music would be more productive and spend more money. In fact, nobody knows what effect playing muzak in shops has on profits. It is simply something that everybody does. But we are learning more about the effect of constantly repeated hearings of songs on the people who have to hear them all the time. Research shows that repeated hearings of complex pieces of music bring greater enjoyment before becoming tiresome. And that point come much sooner with simple songs. 'That's especially the case with tunes that are already familiar. Once that tipping point3 is reached, repeated listening become unpleasant, says Professor John Sloboda of UK's Keele University's music psychology group. 'And the less control you have over what you hear, the less you like it. That's why police forces in the US often try and resolve hostage situations by playing pop songs over and over again at high volume. Eventually, it becomes too much for the criminals to stand and they give up. The problem gets particularly bad at Christmas, when the muzak consists entirely of the same few festive tunes played over and over again. What makes it worse for the shop workers is that they already know these runes. They get bored very quickly. Then they get irritated. Then they get angry. Shop workers in Austria recently threatened to go on strike for the right to silence. 'Shop workers can't escape the Christmas muzak. They feel as if they are terrorized all day. Especially 'Jingle Bells'. It arouses aggressive feelings,' said Gottfried Rieser, of the Austrian shop worker's union. It is not just shop workers who complain. A survey this year by UK recruitment website Retailchoice. com found that Christmas is not only the most testing time for shop workers, but that almost half had complaints from customers about muzak. And the British Royal National Institute for the Deaf estimates that some stores play Jingle Bells 300 times each year. 'That's acoustic torture, says Nigel Rodgers of Pipedown. A group against muzak. 'It's not loud but the repetitive nature causes psychological stress. ' The group wants the government to legislate against unwanted music in stores, hospitals, airports, swimming pools and other public places, claiming it raises the blood pressure and depresses the immune system. Perhaps groups like Pipedown don't really have much to complain about. After all, surely the real point is that people have money to spend. Why complain about a bit of music? The shop workers in the Western world are glad when Christmas is over because they don't have to