Why Do You Lie? The Perils of Self-Reporting

I am always surprised at how easily, and cheaply, we humans lie.

Have you ever been in a conversation about, say, a particular book and been tempted to say you’ve read it even though you haven’t?

I am guessing the answer is yes. But why would anyone bother to lie in such a low-stakes situation?

The book lie is what you might call a lie of reputation: you are concerned with what other people think of you. Of the many reasons that people lie, I have always thought that the lie of reputation is the most interesting — as opposed to a lie to gain advantage, to avoid trouble, to get out of an obligation, etc.

A new paper by the economists Cesar Martinelli and Susan W. Parker offers some fascinating insights into lies of reputation. It is called “Deception and Misreporting in a Social Program,” and will be published soon in the Journal of the European Economics Association.

Martinelli is a Peruvian-born, U.C.L.A.-educated economic theorist who teaches at I.T.A.M. in Mexico City; Parker is an American-born economist, educated at Yale, who also teaches in Mexico City, at C.I.D.E..

Their paper takes advantage of a remarkably rich data set from Oportunidades, a Mexican welfare program. It records the household goods that people say they have when they are applying for the program and then it also records the household goods that are actually found to be in that household once the recipient’s application has been accepted. Martinelli and Parker worked with data from more than 100,000 applicants, representing 10 percent of the applicants interviewed that year (2002).

It turned out that a lot of people underreported certain items that they thought might exclude them from getting benefits. Below is a list of underreported items followed by the percentage of recipients who owned a certain good but who said they didn’t:

Car (83.10 percent)
Truck (81.71)
Video recorder (79.73)
Satellite TV (73.91)
Gas boiler (73.12)
Phone (73.12)
Washing machine (53.46)

That’s not very surprising: you might expect people to lie to gain the advantage of a welfare benefit. But here’s the surprise. Below is a list of household items that were overreported — i.e., which applicants said they had but in fact did not (again, followed by percentages):

Toilet (39.07 percent)
Tap water (31.76)
Gas stove (28.56)
Concrete floor (25.41)
Refrigerator (12.05)

So 4 out of 10 applicants without a toilet said they had one. Why?

Martinelli and Parker chalk it up to embarrassment, plain and simple. People who were desperately poor were also apparently desperate to not admit to a welfare clerk that they lived without a toilet or running water or even a concrete floor. This is one of the most amazing lies of reputation I can imagine.

It should be noted that there is a lot of incentive to lie to get into the Oportunidades program, for the cash benefit equals about 25 percent of the average applicant household’s expenditures. Furthermore, the penalty for underreporting was not very strong: many of the people found to be underreporting goods like satellite TV’s and trucks were were not kicked out of the program. You could argue that the penalty for overreporting, meanwhile, was greater since it might mean being excluded from the program in the first place — which makes the overreporting even more costly.

The Martinelli-Parker paper may have broad implications for not only poverty programs but any kind of project where the data are self-reported. Think about the typical survey on drug use, sexual behavior, personal hygiene, voting preference, environmental behavior, etc.

Here’s what we once wrote, for instance, in an article about the lack of hand hygiene in hospitals:

In one Australian medical study, doctors self-reported their hand-washing rate at 73 percent, whereas when these same doctors were observed, their actual rate was a paltry 9 percent.

We’ve also written about the subjects that online daters are most likely to lie about, and the risky business of election polling — especially when the issue of race is involved.

But as often as we or anyone else writes about the perils of self-reporting, the Martinelli-Parker paper really gives the whole topic a foundation to stand on. Not only does it deliver a surprising insight into why we lie, but it is also a sobering reminder to naturally distrust self-reported data — at least until some scientists enable us to peer into one another’s minds and see what’s really going on there.

I am interested in hearing from readers what kinds of lies you tell, and why.

[Note: I’ll be discussing this topic early tomorrow (Tues.) morning on the new public-radio program The Takeaway.]


Big Rob #121, perhaps you should sleep with more men...? Unfair of you -- and inaccurate -- to distinguish between the sexes when it comes to lying. #97's got it right. :)


- AaronS (#4)

I think you and your pastor may be missing the point... People seem to have a problem with lying more because it involves deliberate deception, not because the lie is just "untrue." So while your pastor didn't make any false claims necessarily, he was tactful enough to know that what he said would be interpreted contrary to the reality.

I'm not saying what he did was wrong though...the explanation just seems a bit too literal.


Like some other people said, I can't imagine lying about whether I have read a book - it seems terrifying to have to fake my way through additional conversation after doing that, and for no reason at all. I like to say that I mean to read it, and I don't really feel bad if I mean to read it in the very distant future. I mean to read everything eventually. And saying you haven't read it allows you to propel the conversation forward by asking, "would you recommend it to me?" (Bonus: if they are lying about having read it themselves, this will make it hurt a little.)

I have tried to cut down on lying for social lubrication purposes, and it's kind of a fun challenge - how can I tell the truth without creating awkwardness? Sometimes it works, sometimes it doesn't, but it gets easier. For example, if I were the woman above who doesn't like meat for various reasons, but isn't a vegetarian, I wouldn't tell my whole backstory about it, but might say, "Actually, I'm a faux vegetarian - meat just doesn't agree with me most of the time, so I order a lot of vegetarian food. But of course I love bacon!" and 99% of the time the person will agree, because people seem to love talking about how they like bacon. And then you just talk about that all night and you're set.

Although now I'm wondering whether people are lying to me and I'm alone in the world on that one. A lot of other people really do like bacon, don't they?



"An honest buck for an honest days's work..." Thousands of innocent Americans killed and still dying Iraq, the US Ecomony in tatters and heading towards the toilet bowl downswirl of complete ruination, the US Dollar replacing toilet paper, countless jobs outsourced, our Supreme Court still acting like Ostriches, Americans reviled, despised, and held in utter contempt by the rest of the world, our kids spoiled rotten ADD imbiciles, more than half the population obese, health care out of control and unaffordable to a hundred million Americans, - just imagine what America would be like if we the President, his administration, and all of his corporate cronies were liars. Natalie

Ed H

I don't exactly lie so much as I embellish. I try to make things a little more exciting than the plain facts would suggest. Often, the embellishment expresses more completely my feeling of something. "I'm having a little party." when "in fact" my daughter and her boyfriend are coming for dinner - and we'll probably drink a little too much and have a few laughs. So it's true that I'm having a party, but if I told the plain truth it would not sound so exciting - or it would be unacceptably verbose.

I also over-report my timesheets - a little bit. But the whole truth is that I have lain awake thinking - or fuming - about work, and I figure I should get paid for that, at least a little bit.

I also dis-embellish (sp) in that I'll say "I had a couple of drinks" when the plain truth is I got a little smashed. Or - yeah ok - just plain smashed is the whole truth there.

Rob O'Matic

A book I've really read (Twice!) called "Dark Horse" by Doug Richardson concerns a Texas gubernatorial race with a Candidate From Hell (Not like any real Texas race)

Anyhow, in a rare moment of honesty, the CFH is telling a reporter how impossible it is to know the truth. "All the truth you need to know is what the other feller knows. You hear my words now. I'm tellin' you somethin'. You don't know if it's true or not, but it SCARES ya. And that's all the truth I need to know!"


This is rather a light and brezzy discussion of lying, but a caution:

There is a very serious side to "lying" which very few people are aware of. This is the additional power that the Federal Government has given itself under Title 18 Section 1001. Under this law you can actually go to jail for lying to ANY federal employee. You are not required to be under oath, it doesn't necessarily have to be connected to any judicial proceeding AND the federal employee doesn't even have to record your statements. Lawyers are advising their clients to NEVER grant any interview to ANY federal employee without the benefit of counsel present. Pretty scary? You bet! I ureg you to Google "Lying to a Federal Agent" to find out more about the incredible scope of the power the government now has over you.


I have been lying to my wife about my actual age since we first met. I am 31, but she thinks I am 34. This is because she herself is 32 and I had read somewhere (10 years ago) that women are less attracted to men younger than themselves. As a result I have to carry this lie now to my grave - as I have done so for the last 7 years. You don't want to know what lies I had to engineer to get around the passport problem!


Looks like we need another column - regarding how easily (and lamely) we justify our lying. Of course, we _never_ do it for "bad" reasons!

Barbara S. G.

I never lie about what I have read or movies, plays, concerts I have attended. I find that pointless. I have lied to the pediatrician about taking my baby's temperature (rectally!) at 3:00 a.m. After 3 kids, I learned to say "she has a temperature of 103!" This gets one a very quick appointment. I have also lied to the gas company (I think I smell GAS) to get them to service my water heater. Am I proud of this? Hmmmm. Well I am not ashamed of the fact that I didn't probe my poor baby's bottom when she was already clearly quite feverish and miserable. The gas company found Carbon Monoxide leakage so maybe I have esp, because although I couldn't smell it, it was there.


Ever heard of tact?

Most of the situations that have arisen so far can be addressed with tactful honesty rather than lies or blunt honesty; and the results are much better for the recipient.


Does my bum look big in this?
Lie: No, you look like a supermodel!.
Blunt honesty: Yes, you look like a whale.
Tactful honesty: The cut/colour/fabric of that outfit doesn't seem to work for you - perhaps try the darker colour/this other cut etc?

Why you were late to dinner:
Lie: I had a flat tyre.
Blunt honesty: I was playing WoW.
Tactful honesty: My time management skills are a bit off today.

Lie: I'm sorry (me) isn't here.
Blunt honesty: F** off.
Tactful honesty: No thank you.

The book thing:
Lie: Yes I have, but it was ages ago.
Blunt honesty: No.
Tactful honesty: Sounds interesting - what's it about?

Your friend with bad breath:
Lie: What bad breath?
Blunt honesty: Your breath stinks.
Tactful honesty: Your breath's been smelling a little different lately, have you been eating different foods? Is your health OK? Perhaps you should get it checked out.


What About Mom

I'm not a fancy economist, so the over- and under- reported percentages confuse me. With my poor powers of reasoning, it seems that there's overlap, such that at least some of the people without toilets DO have the following:

Phone (13 percent)
Car (23)
Truck (21)
Video recorder (19)
Satellite TV (13)
Gas boiler (13)

And it seems like this is a common problem with public assistance. Why would people without toilets be buying these other things, only one of which is a necessity (the gas boiler).

Am I just misunderstanding the whole thing?


i don't lie either.
sometimes i wish i did, but i don't.

i am, however, as the author states, amazed at how easily, and cheaply, other humans do.

wonder if this is why i like dogs a hell of a lot more than i do people?


I read somewhere that people lie more often when they "panic" or when something/someone catches them by surprise. For example, a doctor panics if you ask her about his last hand wash, a student panics when a teacher asks if she knows something, etc. Greetings.

Rich Beckman

"So 4 out of 10 applicants who didn't have a toilet said they did."

I agree with Phil that that is not correct. We don't know how many applicants did not have a toilet.

But I think Phil's "4 out of 10 applicants who said they had a toilet actually didn't" is also incorrect. We don't know how many applicants said they had a toilet.

4 out of 10 of all applicants falsely claimed to have a toilet.

Big Rob

Now I'm ready to take some heat - I will check back later to see how much of it came, alright, here goes: woman lie as if it were their natures - almost everything they seem to say, in the realm of the personal, is a lie, or at best, a "half truth". Mendacity suits them and they don't feel guilt, shame or remorse over it, no matter the consequences. I say this from vast decades of broad (pun intended) experience with the fairer sex, and I report it as a solemn truth. As the saying goes: sad, but true.


I lie to wife about my husband.

Rich Beckman

The last lie I can remember telling was when I told a customer that I attended church (I'm agnostic). I just was not up to listening to the efforts he would certainly make to save me.


I never say I read I book I haven't. I've read enough books to feel secure in saying that I haven't read a very obvious one. In fact I enjoy telling people I haven't read something especially if it's the book of the moment. But now that I think about it, I only read half of Freakonomics and confidently say that I read it.

The easiest tell on a "I've read that book" lie is the follow up, before you can say anything, "but it was years ago. I barely remember it." Liar!

Benita Franklin (alias)

We in America have a problem with lying- Remember, "honesty is the best policy." My dad would say that again and again and again and I believed him. Then when I found out that he really didn't mean it a good deal of the time, what a blow to my idealism. But not all people are like Americans. In many traditional cultures lying is a way of life i.e., honesty is not policy.

I used to have a friend from Columbia South America. She enjoyed having parties and would have one from time to time. But the time factor was always a problem for me. She would say come at 6. What she really meant was come at 8 or 9. (a white lie, but oh how it bothered me when I arrived at 5:45 only to find out that I was 3 hours early.

Come to think of it my European Grandma Rose used to lie when asked a question about food. She would always exagerate in one way or another. (Oh, I only put a bit of sugar in the cake, when she put in a cup or two. It was kind of funny. Guess coming to America did not alter her traditional mind-set.