Engaging in multiple tasks -- such as emailing on Blackberry and talking on the phone while wondering what to cook for dinner -- may not hold good for working mothers anymore, as a new study suggests that multi-tasking is mentally damaging.

'The bottom line is that you can't simultaneously be thinking about your tax return and reading an essay, just as you can't talk to yourself about two things at once,' the Telegraph quoted David Meyer, director of the Brain Cognition and Action Laboratory at the University of Michigan, USA, as saying.

'People may think otherwise, but it's a myth,' he added.

Meyer says that even habitual multi-tasking may overexcite the brain, rendering it unable to focus properly.

'People lose the skill and the will to maintain concentration,' he says.

Meyer's comments come at the time when experts have been worrying about poor grades secured by many children at schools as a result of multi-tasking -- such as listening to music on their iPods, watching television and doing their homework simultaneously.

The researchers even went on to insist that multi-tasking enormously affects the whole family, even though it has always been associated with working mothers. 

'About half the time, children ignore their father or do not stop what they are doing because they are multi-tasking with various electronic gadgets,' said Elinor Ochs, the director of the Centre on Everyday Life of Families at the University of California, USA.

The researchers say the way people have started to divide their focus has become a cause of concern especially for children, as it adversely impacts the way they learn and socialise.

'Children that are instant messaging while doing homework, playing games online and watching television are not going to do well in the long run,' said Jordan Grafman of the National Institute of Neurological Disorders and Stroke.

'Some students cannot go a few minutes without talking on their mobile phones,'