MANY of us would have encountered a colleague with a heightened sense of power who gets a real kick out of demeaning others - the workplace bully, in other words.

There may just be such a jerk or two lurking in your workplace, waiting to sap the chosen few of their energy and motivation, while making their lives miserable.

Clearly, such people have serious self-esteem problems.

The bully "needs to dominate and cause hurt in order to feel in control", said Dr Elizabeth Nair, lead psychologist and chief executive of Singapore-based Work and Health Psychologists.

"Actually unsure of his own self-worth, he tries to establish this with such behaviour that seeks to put down another person," she added.

These bullies may have been "victims" previously, and are now trying to assume the "powerful" role.

It is worth noting what Professor Robert Sutton, an organisational psychologist at Stanford University, once said: "The best test of a person's character is how he or she treats those with less power."

Lest you think the jerks are always someone else, Prof Sutton said it could be any one of us.

Research shows that people change overnight when they are put in positions of power. The result: a newly minted jerk.

"They start talking more, taking what they want for themselves, ignoring what other people say or want, ignoring how less powerful people react to their behaviour, acting more rudely, and generallytreating any situation or person as a means for satisfying their own needs," Prof Sutton has said previously.

So it pays to be mindful of your actions. But how do you know you are actually being bullied at work?

Your boss may have just yelled at you, and you feel victimised. But that does not necessarily constitute bullying.

"The first step is to differentiate a 'tough management style' from 'bullying'," said Ms Deepali Chaturvedi, head of South-east Asia operations at Reed Specialist Recruitment.

"In Asia, a tough and demanding management style is commonly seen and accepted as a standard way to manage subordinates and improve their performance."

But, she added: "Bullying by nature is malicious, with no positive outcome for either the perpetrator or the recipient, and as such should never be tolerated."

Professor Dennis Driscoll, who was invited by Fuji Xerox to give a talk here in July on corporate social responsibility, noted: "Workplace bullying refers to persistent, hostile behaviour against a worker, usually by someone in a more superior position."

These bullies do not just target everyone; they choose who to attack.

The easy prey are the ones who are not in a position to retaliate. They are more likely isolated - physically, socially or emotionally, said Dr Nair.

Threats or insults may be dispensed freely, and there may be unwelcome teasing or social isolation when you find yourself excluded from a gathering.

You may be being bullied if, for instance, your boss is always finding fault with you despite you having delivered well, or he schedules last-minute meetings on the days when he knows you have to pick up the children.

"Bullying can also take the form of humiliation through such things as the imposition of impossible work deadlines or the allocation of meaningless tasks," said Prof Driscoll.

If you are being targeted by a workplace bully, you will know it, because the wound it causes is not just skin-deep. You will feel down, may lose your appetite, and your health may even be affected.

"Job-related effects can range from lower job satisfaction and work productivity, to increased counterproductive work behaviour and intentions to quit the job," said Dr Sandy Lim, assistant professor of management and organisation at the National University of Singapore Business School.

Bullying is also likely to have a negative impact on the victims' mental and physical health.

They may take more sick leave, for example, and these negative effects can also spill over to the employees' personal or family life, she said.

Workplace bullying is obviously unacceptable, and needs to be stopped.