Opinion polls find that two out of five adults and seven out of 10 teenagers believe they watch too much television, and about 10 per cent of adults consider themselves addicted. But what’s interesting psychologically is what happens when they try to stop. Trying voluntarily to stop doing something you claim you are not addicted to can be uncomfortably instructive (it’s often the best way to prove to an alcoholic that he or she does have a dependence problem).

In experiments, many families who volunteered to stop watching - or were even paid to stop - were unable to complete the agreed abstinence period, usually a week or a month. Some fought, verbally and physically, and typical comments included: “The family walked around like a chicken without a headI screamed constantly.” “Children bothered me and my nerves were on edge. Tried to interest them in games, but impossible. TV is part of them.”

But if it is difficult to replace TV in our lives, does that mean the box is bad for us? Yes, say Yale University scientists who recently found that heavy TV viewing contributes to a reduced attention span, diminished self-restraint and impatience with the delays of daily life.

Psychologists also found disturbing results when they compared remote communities before and after the introduction of TV. Over time, adults and children in these towns become less creative in problem-solving, less able to persevere in tasks and less tolerant of unstructured time.

Given the myriad of other activities we could pursue, why is TV so engaging? The answer seems to lie in our brains’ hard-wiring; it appears we are genetically designed to fall in love with TV. We’ve survived because we’ve taken notice of unusual or novel stimuli. Not to do so thousands of years ago might have meant ignoring a lion bounding toward you. So a built-in sensitivity to movement is part of our evolutionary heritage.

Psychologists have found parallels between televisual devices such as cuts, edits, zooms, pans and sudden noises and the kind of stimuli most likely to grab our attention. Even the psychologists who study TV, and are aware of its addictive potential, admit they find it difficult to ignore a set that is on in a corner of the room, even when they are talking to someone else.

There is a happy ending. As with all addictions, the first few days of doing without are the worst. After that, things get easier. But in a society where we spend so little time in community activities, precisely because we are all locked away watching TV, paradoxically the only thing we have in common is what programmes we’ve seen.

Part of the secret to kicking an addictionis to replace the habit. Trying to do without the thing that has been holding together your life can make the days seem full of large, unfilled holes. The essential question is: what else would you like to do? Instead of talking about last night’s telly as a way of bonding with your pupils, encourage conversations about the other interesting things we could do if we weren’t wasting our lives in front of the box. After all, people can be divided into two kinds: those who do and those who just like to watch.

Dr Raj Persaud is a consultant psychiatrist at the Maudsley hospital and senior lecturer at the Institute of Psychiatry in London. He is a fellow of University College London, and author of From the Edge of the Couch published by Bantam Press, pound;12.99. Email: rajpersaud@tes.co.uk