Bayesian Truth Serum: A Simple Trick To Catch Liars

Have you told a lie yet today?  Did you just lie about your answer to that question?  According to this study, the average number of lies consciously told per day by participants was 1.65.  This number seems low to me and it’s likely because people lie about how often they lie in these studies.  Regardless, my point is simply that myriad lies are hurled at you on a daily basis (and this doesn’t include what Harry Frankfurt calls “bullshit” either).

Relax, all this talk about lying isn’t meant to get you all worked up.  Lying and sophistry are natural and perfectly normal behavior for socially intelligent simians.  It’s theorized, that our ability to lie evolved as an important part of how we communicate with each other.  Most of us learn how to lie at a very early age and, according to this article, “lying is actually proof of cognitive development”.

Whatever the reason, I suspect that I have a proclivity to tell the truth more often than I should.  Even so, I think one of the worst pieces of advice I’ve ever heard is the following: don’t ever tell a lie.  If a female has ever asked you if she looks fat in a certain pair of pants you already intuitively know why.  Lying is not only acceptable in some situations, it can even be the right thing to do.  This is partly why I can’t classify myself as a deontologist.  I’m not sure of much, but when a female asks “Do I look fat in these pants?” I’m pretty confident that lying is the right thing to do.

With that being said, I still think it’s a valuable skill to know when you are being lied to.  In fact, sometimes it can be incredibly difficult to sniff out lies.  Alas, there is a tool to help improve your ability to do this in some domains. I was recently reading Discover Your Inner Economist and the author, economist Tyler Cowen, mentioned something called Bayesian truth serum (“Bayesian” may be a stretch here, but it sure sounds cool!).  In essence, this means that to get a more truthful answer from someone it is more useful to ask for their opinion on what they think other people do than it is to ask them what they do.

For example, one is more likely to home in on the truth if they ask a person “How many sexual partners do you think the average man/woman has had?” versus “How many sexual partners have you had?”.  The reason is due to the availability heuristic.  If a single man was asked the latter question by an attractive woman he’s likely to quickly concoct a lie to make himself look better to her.  However, if she asked him the first question mentioned above instead, he would use the mental shortcut of referencing his own number.  Interestingly, he will likely think his own number is indicative of the average person (even if it isn’t).

Who needs a lie detector when you have Bayesian truth serum?

The Sexual Ambition of Genghis Khan

What percentage of your ancestors were men?  I’ll give you a hint, it’s not 50%.  According to Roy Baumeister, author of Is There Anything Good About Men?, it has been confirmed via genetic evidence that today’s human population is descended from roughly twice as many women as men.  Baumeister has called this the “single most under-appreciated fact about gender.”  You may be wondering: how can this be?

Not all men bring value to the sexual marketplace, but nearly all females do.  To drive this point home, imagine life on two different islands.  The first island has 999 men and one woman and the second island has 999 women and one man.  Which island civilization could create more offspring and provide the species with a better chance of survival?  It becomes obvious that the services of most men aren’t needed, but nearly all females add reproductive value.

While it’s certainly true that it takes a man and a woman to reproduce, one sexually ambitious man can father thousands upon thousands of children in a lifetime, while an individual woman is lucky to have a dozen children in a lifetime.  Since most females get to reproduce they seem to be more egalitarian (and less violent) by nature.

Here’s another interesting fact: roughly 16 million men alive in Central Asia today are the direct descendants of Genghis Khan (confirmed by their possession of his unique Y chromosome).  Whatever else may be said about Genghis Khan, one cannot deny that the man had sexual ambition.

In their book, The 10,000 Year Explosion, anthropologists Gregory Cochran and Henry Harpending tell us what Genghis Khan’s definition of “supreme joy” was: “to cut my enemies to pieces, drive them before me, seize their possessions, witness the tears of those dear to them, and embrace their wives and daughters!”  Apparently, he and his sons seemed to find that last part of the definition especially joyful.  According to Cochran and Harpending, “He and his sons and his son’s sons — the Golden Family — ruled over much of Asia for several hundred years, tending to the harem throughout.  In so doing, they made the greatest of all genetic impacts.”

These two facts I’ve laid out are obviously very important to consider when analyzing the motivational differences between men and women in the modern world.  So what does this tell us about our men today?  Well, disheartening as we may find it, today’s men are disproportionately descended from the likes of Khan.  The men who lacked this type of sexual ambition (and the ability to compete) often failed to reproduce at all.  Their “bad” genes, then, ended up in an evolutionary cul-de-sac.

Most of us rightfully find Khan’s behavior odious.  However, Khan (and his ilk) can explain why nice guys finish last in evolutionary terms.

Humans Are Going the Way of Draft Horses

In his essay “Darwin Among the Machines” Samuel Butler wrote: “The machines are gaining ground upon us; day by day we are becoming more subservient to them; more men are daily bound down as slaves to tend them; more men are daily devoting the energies of their whole lives to the development of mechanical life.  The upshot is simply a question of time, but that the time will come when the machines will hold the real supremacy over the world and its inhabitants is what no person of a truly philosophic mind can for a moment question.”

So the machines are starting to get really good.  If you’re not yet convinced of that, consider the fact that Google’s robotic cars have now safely completed more than 200,000 miles of computer-led driving.  Barring any major legal and cultural holdups, it’s possible that jobs like driving cabs and trucks will be obsolete within a decade.  That machines are displacing human workers is not necessarily a bad thing though.  In many ways, this is a sign of economic progress.  However, economic progress often comes with unintended social costs (e.g., unemployment).  If we think about humans as racing against machines for jobs, then some of the evidence shows that many people appear to be already losing the race.

As early as 1821, the economist David Ricardo recognized that unpleasant consequences will befall on an economy when machines become directly substitutable for human labor.  Historically, however, this hasn’t happened and people who fear that machines take jobs from humans are accused of believing in the Luddite Fallacy.  Despite the fears of Ned Ludd (and the Luddites), machines have been a complement to human labor through the entirety of the 20th century.    Will this be true in the 21st century though?  If not, then machines will likely cause what John Maynard Keynes famously called the disease of “technological unemployment” in his essay “Economic Possibilities For Our Grandchildren“.

An interesting question to consider is the following: exactly whose jobs are the machines going to the take?  Perhaps there is a lesson to be learned by studying the “working horses” of the 18th century.  In Gregory Clark’s book A Farewell to Alms he wrote:

there was a type of employee at the beginning of the Industrial Revolution whose job and livelihood largely vanished in the early twentieth century. This was the horse. The population of working horses actually peaked in England long after the Industrial Revolution, in 1901, when 3.25 million were at work. Though they had been replaced by rail for long-distance haulage and by steam engines for driving machinery, they still plowed fields, hauled wagons and carriages short distances, pulled boats on the canals, toiled in the pits, and carried armies into battle. But the arrival of the internal combustion engine in the late nineteenth century rapidly displaced these workers, so that by 1924 there were fewer than two million. There was always a wage at which all these horses could have remained employed. But that wage was so low that it did not pay for their feed.

I recently finished reading Erik Brynjolfsson’s and Andrew McAfee’s book Race Against The Machine, which, by the way, was quite good.  In one section of the book they make the claim that “It can be easier to automate the work of a bookkeeper, bank teller, or semi-skilled factory worker than a gardener, hair dresser, or home health aide.”  This insight is taken from Moravec’s Paradox, which, according to Wikipedia, states that “high-level reasoning requires very little computation, but low-level sensorimotor skills require enormous computational resources.”  In other words, jobs that require vision, fine motor skills, and locomotion have been much harder to automate than ones that require fairly straightforward information processing.

I think the 21st century’s draft horses are the workers whose jobs don’t involve any innately human skills, like creativity.  Strangely, many of the jobs in danger of being lost to machines would be considered by many to be “white-collar” jobs.  For what it’s worth, I take one of Brynjolfsson’s and McAfee’s central claims very seriously, i.e., it’s not wise to try and compete with the machines.

The Economics of Gift Giving

Here’s something interesting to consider: if we really care about our loved ones’ best interests, we ought to reconsider giving them gifts other than cold hard cash.  I already know what you’re thinking — giving cash, how tacky!  How can it possibly be better to give our loved ones cash instead of gifts?  This may sound strange to the non-economist, so allow me to explain.  Before reading on though, please heed the following warning: I don’t generally recommend taking romantic advice from economists.  You’ve been warned.

So here’s the issue: gift giving (non-cash gifts) is often a potential source of what economists call deadweight loss.  According to the theory of consumer choice the consumer (i.e., the receiver of the gift) knows more about what will maximize their utility than the gift giver does.  Accordingly, if we really care about allowing the receiver of the gift’s ability to maximize their utility, we should only give cash as a gift.

Consider a hypothetical ugly shirt that you received on your last birthday from your great aunt.  Let’s suppose that the shirt was purchased from Gap for $39.99, but let’s also suppose that you only value at, say, $10.  Now, think of all the other things you might like to do with that $39.99 that don’t involve owning an ugly shirt.  The difference between the price of the ugly shirt and the amount you value at it after receiving it is the deadweight loss.  Notice that the deadweight loss destroyed almost 75% of the gift’s original value.  Your estranged aunt who gave you the Gap shirt could have improved your financial welfare by $20.99 if she had simply given you cash instead of the shirt.

Interestingly enough, I recently stumbled across a paper by the economist Joel Waldfogel called “The Deadweight Loss of Christmas“.  In the paper, he conservatively estimates that the deadweight loss of all 1992 gift giving was roughly $4 billion (yes, that’s billion with a “b”).  In Waldfogel’s book, Scroogenomics, he claims that Americans spent $66 billion on gifts in 2007.  However, the gift recipients only valued the gifts they received at $54 billion, producing a near $12 billion deadweight loss.  Holy smokes!


Here, then, is the interesting question: why don’t people give cash as gifts more often?  The reason, I think, is that giving cash signals that one has money and that’s about it.  And gift giving is really all about signaling, not helping others maximize their utility as efficiently as possible.

Giving cash may be the best way to ensure that the gift recipient can maximize their utility, but it doesn’t really signal anything of importance to our loved ones.  I’m not all that wise, but I am wise enough to know that giving my girlfriend a $100 bill for her birthday is not a prudent thing to do.  This is true no matter how romantically I wax poetic about the potential for deadweight loss.  Alas, there is more to romance than efficiency!

To put it simply, anyone can give her cash.  She expects me to signal that I’m closely in tune with her by showing her that I listen and know what gifts she would like.  It’s certainly a possibility that I could make a major financial gaffe when it comes to picking out a gift, but I suspect that my attempt at signaling is more important to her than is my concern that her utility be maximized.  Obviously, if I were to spend $100 on a gift that she valued at $100, it still wouldn’t make her any better off than if I just gave her cash.  This is because she could simply buy the gift with the equivalent amount of cash I gave her.

Is it possible that gift giving is sometimes purely selfish too?  Absolutely!  Giving gifts can be used as a means to control people.  The gift, then, is not a gift at all, but a way to make the recipient feel guilty and in emotional debt.  It sounds sinister and it is.  However, I think it occurs more often than most of us realize.  I think many parents (both strategically and inadvertently) do this to their kids sometimes.  My parents, however, have never done this to me and I’m very thankful for that!

In case I haven’t made it abundantly clear, I don’t think we should give non-cash gifts because we want to help our loved ones maximize their utility.  As I’ve mentioned, giving cash is certainly a more efficient way to do that.  Rather, I think we should give gifts because they can make for great signals.  And sometimes the signals have to be incredibly inefficient or wasteful, otherwise they don’t work.  Ultimately, the practice of gift giving is a terribly inefficient and costly way to help our loved ones; however, it’s an amazingly cheap way to signal how much we care.

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