How can you spot a liar online? Some telltale signs of online deception from Cornell professor of communication Jeff Hancock.
STEWART: All right. He has been studying online deception. So, Jeff, what are the telltale signs of an online liar?
Dr. HANCOCK: Well, it depends on the kind of lie they're telling, but one of the main ones is reduced first-person references. So that's when people talk about themselves. So if I were to say I came to New York yesterday, maybe that would be truthful. And if I said something like got into New York yesterday. Now, you can see I dropped the first person singular there - the I. And that's related to when people tend to be deceptive.
STEWART: But they tend to write a little bit more.
Dr. HANCOCK: They do. And the sites that we've looked at online when people are lying, they use more words, which is a little bit strange, but we think that it's because they're really trying to convince you of their lie. And because they can type and take their time to do it, they take more words and use more words to convince you.
STEWART: We were talking earlier, and I said I had done a story about how little kids learn to lie. And they learn early on to lie to avoid punishment. If self-preservation is part of lying, you don't want to tell your boss you messed up on the report because you're afraid you're getting fired or docked…
Dr. HANCOCK: Mm-hmm.
STEWART: …what kind of punishment are people afraid online that they would lie about who they are and their accomplishments?
Dr. HANCOCK: Right. Well, most of our online activities are social. So, yeah, we use it to search for information, but we also use it to communicate with our friends, talk about who we are and do things together. So the number one punishment when you get caught lying online is ostracism. You are worried about people thinking that you're a bad person and not wanting to talk to you anymore.
STEWART: Or maybe in the case of some of these dating sites, that you're not as attractive…
Dr. HANCOCK: Right.
STEWART: …as you might present yourself to be.
Dr. HANCOCK: Exactly. If you lie too much, then when you actually meet the person, that's going to be a problem. And as my friend from MIT, Dan Early(ph), says, with online dating, you need to lie enough to get to coffee, but not so much you don't get to bed.
(Soundbite of laughter)
STEWART: A guy at MIT said that?
Dr. HANCOCK: He's a funny guy.
(Soundbite of laughter)
STEWART: When people do put together these dating profiles, what kind of things do they lie about and why?
Dr. HANCOCK: Well, people tend to lie a lot in their profiles - everybody. And what we looked at were things like height and weight and age, so body and age things. And we also looked at income and status. But we found that men tend to lie about their height, and they would do what I call a strong round-up. So, if they achieve an inch, they'll add another inch. So, 5'9" and one-tenth, they'll go up to 5'10". Women tend to lie about their weight.
STEWART: I'd say age or weight....