Robert Feldman, dean of the College of Social and Behavioral Sciences and professor of psychology at the University of Massachusetts, is the author of The Liar in Your Life: The Way to Truthful Relationships. Here, he discusses why we lie, what we lie about, and why even the whitest of lies can be damaging.

Q: Why do we lie?

A: The reality is that lying is a kind of social lubricant. It allows us to converse with other people in a fairly smooth and easy way and to avoid going into all of the details if we were being 100 percent accurate all of the time.

Another reason we do it so often is due to a phenomenon known as "the liar's advantage." One of the reasons we lie is because we get away with it. People are not very good at detecting lies, even though we commonly think we can. Most people can only detect lies at about a 50 percent chance rate – so you might as well flip a coin. The other thing is that very often we want to be lied to; we want to hear things that are consistent with our self-image. We let people tell us the things we want to hear without confronting them because it helps us build our self-image as above average.

Q: Do people lie more frequently than we think they do?

A: Absolutely. Most people lie considerably more than we usually expect. Most of us think the lies we encounter in our everyday lives are fairly rare and occur in unusual circumstances and in places like car dealerships, but the reality is that we're lied to on a fairly frequent basis. My research shows that when people are getting to know one another, the average number of lies in a 10-minute period is three; and some people lie as many as 10 times in that period. Most of the time the lies are fairly benign – what we call "white lies" – but in some cases they're a little more insidious.

Q: Are people more likely to lie to someone they're close to or more likely to lie to a stranger or acquaintance?

A: They're more likely to lie to people they're just getting to know and to people they don't know very well. The more we know someone, typically, the less likely we are to lie to them. But when we do lie to someone we know well – particularly in very close relationships, like with spouses and lovers – the lies tend to be very profound. The bigger lies come with the people we know best, and often have to do with infidelity and things of that sort. The lies we come out with when we're just getting to know someone tend to be fairly benign – like, "I agree with you" or "you're right" or lies that are designed to make us look better.

Q: Are those little white lies harmless?

A: I think they're corrosive. I don't think we can make a distinction between white lies and other lies. All lies have a cost. The degree of consistency with which we're lying to other people leads to relationships that are inauthentic. If we start a relationship based on some degree of deception, it can continue into the relationship and we have to somehow admit and repair those lies or we continue the lies. Either way, they're going to be damaging to the relationship. It's very easy for little white lies to lead to larger lies. If we're very good at using lies as a social crutch, we'll probably use them more and more frequently.

Q: Is there such a thing as a good lie?

A: No. Except in extreme cases – like, when the Nazis were at the door and you were lying about who you were harbouring. But in most cases, the truth trumps lying and it's better to tell the truth. It's harder to tell the truth; we often lack the vocabulary to be truthful. When someone asks how you like their tie, it's very hard to say, "It looks terrible." It's much easier to say, "It looks great." We need to develop ways of saying, "Oh, I really like the pattern" and not "the colour's horrible." It's much easier – which is why we do it so often.

Q: Do men and women lie differently?

A: There is a sex difference. It's not that men and women lie in different quantities – they lie about the same amount – but they lie differently. Women lie more to make the person who's talking feel better about themselves, whereas men lie more to make themselves look better. It's consistent with gender roles as society sees them. Women tend to be more concerned about relationship maintenance and making sure relationships move along in a smooth way, and men are more apt to want to make themselves look good and powerful and more competent.

Q: What advice do you have for dealing with a liar?

A: I think it's important to ask people to tell you the truth. You have to constantly confront liars. When you ask someone what they think of your tie, tell them you really want to know the truth. And we have to be ready to accept what it is we're going to hear. We live in a culture of lies and it's so easy and acceptable to lie. But I think it's very important to demand the truth from others, as well as demanding the truth from ourselves.