Every modern office worker knows the drill: the email queue is full, the telephone is ringing and the boss is bearing down on your desk from across the open-plan office. Multi-tasking is the order of the day.

Distractions prompt the thought to cut yourself off to work in peace for a while. There is little chance of that in the current working environment which demands the ability to keep several balls in the air at the same time.

Professor Dirk Windemuth, a health and safety at work expert working in accident insurance in Berlin, has little regard for this attitude. Rather do things one at a time and do them properly, is his view. Employees should not deceive themselves into thinking that they achieve more in the same time merely by carrying out several different tasks at the same time, he says. "That's a fundamental mistake."

People are simply not built for multi-tasking, by contrast with computers, which these days frequently have four processors to carryout several tasks in parallel. The human brain is designed for mono-tasking and has to jump backwards and forwards between different tasks - and that takes up time and energy.

For this reason, juggling tasks is ineffective. Workers trying to do several things at the same time take longer, make more mistakes and are more stressed at the end of the day, which results in a decline in performance.

"You perform worse and concentration declines," Windemuth says. The danger is that workers lose concentration when they have to carryon a phone conversation as well and this can lead to having to askfor the information all over again to clear up misunderstandings.

Someone working on a presentation, and trying to deal with their emails at the same time, takes more time than someone who carries out these tasks one at a time, Windemuth says, citing his research.

The interruptions caused by emails can be fatal for a productive train of thought, in the view of Anja Baethge, a psychologist at the University of Leipzig. "Where was I now?" is the question that arises, as the staff member is forced to backtrack to recover lost ground.

In addition, multi-tasking increases the stress level, as staff feel themselves under increasing time pressure if the number of tasks starts piling up in their in-tray, said Baethge, who has drawn up a study on the issue for the German government.

Windemuth sees the flood of information coming from mobile phones, emails, messenger and chat programs, as well as social networking sites like Facebook, as putting workers under increasing pressure to have their eye on a range of inputs.

Distractions have to be reduced, if the main work is not to suffer. One way of doing this is switching off the on-screen pop-ups that flag up that an email has arrived, Windemuth advises. Instead of reading the new message immediately, office workers should discipline themselves to go through their inbox four or five times a day and deal with correspondence in batches.

Another trick is to have a "quiet hour," during which a colleague deals with any distractions. "During this period, someone else picks up the phone, so that you can concentrate on tasks that take a bit longer," he says.

Simply dropping everything is the wrong reaction, unless you're a doctor in the emergency unit, Baethge says. It is essential to deal with interruptions in an appropriate way, "for example by finishing the sentence you are writing before picking up the phone, otherwise the idea is gone." (dpa)