Arrogant, egotistical, deceitful, manipulative, over-sensitive and totally lacking in empathy - just some of the ways you'd expect a narcissist to be described.

But a recent study from Aarhus University in Denmark concluded that some narcissistic traits aren't so terrible. In fact, in the corporate world, female bosses are able to 'exploit the bright sides' of narcissism while tempering its 'dark side' to particularly good effect.

So what are these 'bright sides'?

Dr Ramani Durvasula, one of the world's leading experts on narcissism, explains that several of the traits narcissists possess can almost certainly be beneficial both personally and professionally. 

'Their charm, confidence, innovative grandiosity - if you can pool all the best things you can find in a narcissist and strip away all the bad stuff, then never let them go!' she says. 'You've found something of a unicorn.'

But, she warns, 'I don't actually think there is such a thing as a "good" narcissist. There might potentially be some good ingredients in there - the flour, if you like - but the narcissist is the entire cake, combining all the other less savoury traits, such as the lack of empathy, the entitlement, the arrogance.'

Here Dr Ramani reveals the surprising signs your charming boss – or boyfriend – might actually be a narcissist...

They make you feel like you're the only person in the room 

Narcissists can be incredibly seductive. They not only know how to work a room, but they make you feel like you're the only person in it. 

When they talk to you, it feels like they're focused on you and you alone and they can easily alternate between being a good listener and a confident speaker, often with a good sense of humour too. It tips over into the dark side, however, when their charm feels hollow and transactional, like a switch turned on to win people over and get something from them. 

There's a wonderful scene in the series The Morning Show on Apple TV, where the boss, played by Billy Crudup, is walking backstage and greeting everyone with a cheerful: 'Hey, how are you?' and the second he passes them, his face goes cold. I've never seen transactional charm portrayed so well.

They think outside the box - and won't take no for an answer 

Narcissists are great innovators because they have such grandiose plans for themselves. They won't take no for an answer and don't feel their vision should be limited, and because of that, they push things to the edge and think outside the box. 

They'll create things that seem inconceivable to the rest of us, like a computer we can carry around in our pocket, or a car that doesn't need petrol. These visions are often fantastical, but some grandiose narcissists have the discipline, intellect and skillset to make them happen. 

That willingness to go against convention, and do what others tell them not to do, is a bitter pill the rest of us have to swallow because of the incredible things these narcissistic innovators create. That said, I'm not sure they are easy people to work for or be in a relationship with.

They're deeply ambitious

Certainly, ambition in and of itself is not a problem. When it's realistic and based on discipline and hard work, ambition is healthy. Narcissistic people actually have a tremendous capacity for discipline - but only if it serves them. 

If they're deeply ambitious, they'll focus on that to the complete exclusion of everyone and everything else in their lives - good for their business, perhaps; not so good for their family. 

For narcissistic people, their need to succeed and to achieve stems from the need for a constant supply of reward and praise.

They're good leaders

Not everyone can or wants to lead, but narcissists definitely do. They like to be in charge. The recent Danish study argues that women leaders are better than men at seeing things in a more holistic way. 

The researchers looked at the language narcissistic female bosses used, which was slightly more collective and less exploitative and entitled than that of their male counterparts. They were able to harness the better parts of their narcissistic personality - the focus, the desire to lead - while tempering the bad bits, meaning they beat their narcissistic male peers in terms of corporate performance. 

Wanting to be a leader definitely isn't a bad thing in itself. But when the orientation towards leadership is really intended to bolster one's ego, it can take on a darker, more narcissistic form.

They're flexible with the rules  

People who are more agreeable are much more likely to stick to rules - they'll always put their shopping trolley back, they'll never park where they're not supposed to and they'll queue patiently. Narcissistic people, on the other hand, are too entitled to follow the rules.

Yet there is a healthy rule-breaking quality, for example, when a rule seems arbitrary or ridiculous, such as not being able to park in a completely empty car park. The willingness to be flexible enough to say: 'Come on, let's work around this!' can be a good thing. Where it isn't good is when the narcissist breaks the rule because they believe they shouldn't have to follow it but everyone else should.

... and they may keep breaking the rules, until they face real consequences

When we think of the grandiose narcissist who has a big dream of inventing some tech device and works 18 hours a day, sleeping in his office just to get the job done, there's almost a manic discipline to it. 'I'm going to get this done to the negligence of everything else.' 

And then they produce something world-changing. But when that persistence becomes what we call 'perseverative', fixating on an idea so intensely, that's when things go wrong. To be perseverative means doing the same thing over and over again, sometimes when it's not even working, and in the process, wearing down the people around you. 

Narcissists will then lash out and get very angry because things aren't going their way. And no one, of course, would describe that kind of behaviour as a 'bright side'. 

As told to Lina Das. Dr Ramani's book, It's Not You: How to Identify and Heal from Narcissistic People is available now. For more information see doctor-ramani.com