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My daughter was learning about prime numbers and she had an exercise to identify all the prime numbers less than 100.  I made a little game out of it with her by offering her 10 cents for each number correctly categorized as prime or composite within a fixed total time.

As she progressed through the numbers I noticed a pattern.  It took her less time to guess that a number was composite than it took her to guess that it was prime. And of course there is a simple reason:  you know that a number is composite once you find a proper factor, you know that a number is prime only when you are convinced that a proper factor does not exist.

But this was a timed-constrained task and waiting until she knows for sure that the number is prime is not an optimal strategy.  She should guess that the number is prime once she thinks it is sufficiently likely that she won’t find any proper factor. And how long that will take depends on the average time it takes to find a proper factor.

In particular, if the average time before she guesses prime is larger than the average time before she guesses composite then she is not optimizing.  Because if that were the case she should infer that the number is likely to be prime simply from the fact that she has spent more than the average time looking for a proper factor.  At an optimum, any such introspective inference should be arbitraged away.


There is a pattern to how people arrange themselves in elevators depending on the number of other passengers. (via The Morning News.)

If someone else comes in, we may have to move. And here, it has been observed that lift-travellers unthinkingly go through a set pattern of movements, as predetermined as a square dance.

On your own, you can do whatever you want – it’s your own little box.

If there are two of you, you take different corners. Standing diagonally across from each other creates the greatest distance.

When a third person enters, you will unconsciously form a triangle (breaking the analogy that some have made with dots on a dice). And when there is a fourth person it’s a square, with someone in every corner. A fifth person is probably going to have to stand in the middle.

I liked the part where it is explained why we are socially awkward in elevators.

“You don’t have enough space,” says Professor Babette Renneberg, a clinical psychologist at the Free University of Berlin.

David Axelrod, a senior campaign adviser for President Barack Obama’s reelection campaign, trash-talked Mitt Romney on Sunday, calling last week’s Republican National Convention “a terrible failure” and claiming Romney did not receive a polling bounce.

Presidential campaign staff are always saying stuff like that.  How badly the other side is doing.  Promoting polls that show their own candidate doing well and dissing polls that don’t.  While that seems like natural fighting spirit, from the strategic point of view this is sometimes questionable strategy.

If you had the power to implant arbitrary expectations into the minds of your supporters and those of your rival, what would they be?

  1. You wouldn’t want your supporters to think that your candidate was very likely to lose.
  2. But neither would you want your supporters to think that your candidate was very likely to win.
  3. Instead you want your supporters to believe that the race is very close.
  4. But you want to plant the opposite beliefs in the mind of the opposition.  You want them to think that the race is already decided.  It probably doesn’t matter which way.

All of this because you want to motivate your supporters and lure the opposition into complacency.  If you are David Axelrod and your candidate has a lead in the polls and you can’t just conjure up arbitrary expectations but you can nudge your supporter’s mood one way or the other you want to play up the opposition not denigrate them.

Unless its only the opposition that is paying attention.  Indeed suppose that campaign staffers know that the audience that is paying closest attention to their public statements is the opposition.  Then right now we would expect to be hearing Democrats saying they are winning and Republicans saying their own campaign is in disarray.

David Levine’s essay is all grown up and now a full-blown book.  His goal is to “set the record straight” and document the true successes and failures of economic theory.  Here is a choice passage:

One of the most frustrating experiences for a working economist is to be confronted by a psychologist, political scientist – or even in some cases Nobel Prize winning economist – to be told in no uncertain terms “Your theory does not explain X – but X happens in the real world, so your theory is wrong.” The frustration revolves around the fact that the theory does predict X and you personally published a paper in a major journal showing exactly that. One cannot intelligently criticize – no matter what one’s credentials – what one does not understand. We have just seen that standard mainstream economic theory explains a lot of things quite well. Before examining criticisms of the theory more closely it would be wise to invest a little time in understanding what the theory does and does not say.

The point is that the theory of “rational play” does not say what you probably think it says. At first glance, it is common to call the behavior of suicide bombers crazy or irrational – as for example in the Sharkansky quotation at the beginning of the chapter. But according to economics it is probably not. From an economic perspective suicide need not be irrational: indeed a famous unpublished 2004 paper by Nobel Prize winning economist Gary Becker and U.S. Appeals Court Judge Richard Posner called “Suicide: An Economic Approach” studies exactly when it would be rational to commit suicide.

The evidence about the rationality of suicide is persuasive. For example, in the State of Oregon, suicide is legal. It cannot, however, be legally done in an impulsive fashion: it requires two oral requests separated by at least 15 days plus a written request signed in the presence of two witnesses, at least one of whom is not related to the applicant. While the exact number of people committing suicide under these terms is not known, it is substantial. Hence – from an economic perspective – this behavior is rational because it represents a clearly expressed preference.

What does this have to do with suicide bombers? If it is rational to commit suicide, then it is surely rational to achieve a worthwhile goal in the process. Eliminating ones enemies is – from the perspective of economics – a rational goal. Moreover, modern research into suicide bombers (see Kix [2010]) shows that they exhibit exactly the same characteristics of isolation and depression that leads in many cases to suicide without bombing. That is: leaning to committing suicide they rationally choose to take their enemies with them.

The book is published as an e-Book by the Open Book Publishers. You can download a PDF for a nominal fee or even read it for free on the website.  Here’s more from David, writing about Kahnemann’s Thinking Fast and Slow.

People are taught to us association as a mnemonic device to help them remember things.  Well it appears you can do something similar to help you forget:

The experiments started with MacLeod and Noreen showing their subjects a series of different words — “barbecue,” “theater,” “occasion,” “rapid,” for example — and then telling them to generate one specific personal memory in response to each word.

There were 24 words in all, and after the subjects had described their memories, they were all sent home and told to come back a week later.

The following week, when they returned, they were given a transcript of each of the memories they’d shared, along with the specific word that had generated it. They reviewed the words and memories until they knew exactly which word went with which memory, and then were put in front of a computer and told that they would see each of those words flash on the computer screen in front of them.

If the word appeared in green, they were to repeat the memory associated with that word out loud, but if the word appeared in red, it was very important for them not to think about the memory associated with that word.

MacLeod and Noreen showed the subjects 16 of the 24 words over and over and over. Each time a subject either repeated the memory or blocked it. Some people apparently pictured a blank; others distracted themselves with other thoughts.

‘A Significant Forgetting Effect’

At the end of this process, the subjects were tested to see if there was a change in what they recalled. And there was — in the memories that had been repeatedly blocked.

“There was a significant forgetting effect, about a 12 percent drop in the level of details recalled,” MacLeod says. “That’s a large effect.”

Via my favorite source for toilet humor, Adriana Lleras-Muney, here is a paper describing how the urinal game and other bathroom customs can be used in introductory Sociology classes.

the use of “interactive exercises” can also be a valuable way by which to underscore the connection between individual actions and social structure. So stated, this paper identifies a number of “everyday” participatory exercises designed to spur classroom interaction and highlight core sociological concepts. Specifically, I use interactional scenarios within the typical American men’s public restroom to emphasize: 1) that individual actions, even those that exist in the mundane, are influenced by larger social-cultural forces; and 2) that a number of core sociological concepts can be found and explored in a place generally ignored or taken for granted.

I wrote about the urinal game here and the trough variant here.

Treatment 1 is you give people a cookie and some cake and you ask them to rate how much they like the cookie better (which of course would be negative if they like the cake better.)

Treatment 2 is you present them with the cookie and the cake and you let them choose. Then you also give them the other item and have them rate just as in treatment 1.

Of course those in treatment 2 are going to rate their chosen item higher on average than those in treatment 1. But let’s look at the overall variance in ratings. A behavioral hypothesis is that the variance is larger in treatment 2 due to cognitive dissonance. Those who expressed a preference will want to rationalize their preference an this will lead them to exaggerate their rating.

Now I wouldn’t be surprised if an experiment like that has already been done and found evidence of cognitive dissonance. The next twist will explore the effect in more detail.

The cookies will be tinged with a random quantity of some foul tasting ingredient, unknown to the subjects. Let’s think of the quantity as ranging from 0 to 100. We want to plot the quantity on the x-axis versus the rating on the y.

My hopothesis is about how this relation differs between the two treatments. At an individual level here is what I would expect to see. Consider a subject who likes cookies better. In treatment 1 he will have a continuous and decreasing curve which will cross zero at some quantity. I.e too much of the yucky stuff and he rates the cake higher.

In treatment 2 his curve will be shifted upward but only in the region where his treatment 2 rating is positive. At higher quantities the curve exactly coincides with the treatment 1 curve.

I have in mind the following theory. There is a psychic cost of convincing yourself that you like something that tastes bad. Cognitive dissonance leads you to do that. But when the cookie tastes so bad that it’s beyon your capacity to convince yourself otherwise you save yourself the psychic cost and don’t even try.

Now we won’t have such data at an individual level to see this. The challenge is to identify restrictions on the aggregate data that the hypothesis implies.

I want to say this would be hilarious if true.  But the thing is it can’t be hilarious even if its true because, not knowing for sure whether its true or a hoax its too easily hoaxed and its exactly the kind of thing that would be hoaxed and having that in your mind when you watch it makes it not funny even if its true.  There is a trough in the funny curve as we move along the x-axis between the two local optima of overtly made-up (e.g. an SNL fake commercial) at the left end-point and true with subjective probability 1 on the right end-point.  Its getting near impossible to make it that far to the right, indeed the farthest we can get still puts us below the local optimum at the left.

(Capotain curl:  Kottke.)

A great story on The Morning News about a guy who is trying to preserve his spoiler-free existence in the face of meddling Internets, bus riders, and Amazon delivery guys:

Well, don’t you worry. This book will be on your doorstep tomorrow afternoon, ready to read.

I, of course, could read the book–YOUR book–right now.

And I gotta admit, it WOULD be fun to be one of the first people in the world to know how it all ends.

Hmm. So, maybe I’ll just read the last page…


Hah hah. I’m just yanking your chain. That’s not how it ends. Or maybe it IS, and I’m just saying it’s not so you’ll be doubly surprised when you finish it. You never know.

I really did read the last page, though. The final word is “haberdashery.” You can verify that when you get the book. Tomorrow. A full day after I had it.

I gotta tell ya, though: Now that I know how it ends, I kind of want to read the whole thing. If I start right now, I could probably finish it and get this book in the mail to you by Wednesday. You wouldn’t mind waiting a few extra days, would you?

Also, I dog-ear pages to save my place. I hope that’s OK.

j/k. I wouldn’t really read this book. 1,000 words about fairies? Yeah, no. Besides, who has the time? Some of us have to work for a living. For instance, I bust my hump 60 hours a week schlepping your books around.

Besides, I’d rather see the movie anyway. That chick who plays Hermione is smoking hot. I’d quidditch, if you know what I’m sayin’.

 Including analysis of the ncessary and sufficient epistemic conditions for an arbitrary statement to qualify as a spoiler:

  • Did your comment spoil my reading experience? Yes.
  • Was my experience any less spoiled because you didn’t know your comment was true? No.
  • Was my experience any less spoiled because you really, truly, honestly, swear to God didn’t mean to spoil the experience for anyone? No.
  • Was my experience any less spoiled because I knew your comment was true only by accident? Nope again.

Read it.  (Spoiler alert.)

Wile E. Coyote runs off a cliff but gravity doesn’t seem to work on him. He just keeps on running, suspended in air, a supernatural feat. But here’s the tragedy: he is capable of this feat only because he doesn’t know he’s doing it. And it’s exactly the moment he realizes there is no ground beneath his feet that he comes crashing down into the canyon below. There is never an instant where he is both flying and aware that he is flying.

It’s the fearless who succeed. But take two people who are equally talented and ask which one is more likely to be fearless. It’s the one who is less worried about failure. But if we turn that around then what it says is that the guy for whom failure hurts the most is the one that’s going to fail.

Everyone has gone through something like this:  you take on some new challenge like playing chess or the piano. You work hard at it because initially two things are true: a) when you see other people who do it well you sense the feeling of pride and satisfaction you would have if you could do it well too, and b) at the beginning you cannot yet do it well. Then after lots of hard work finally you can do it too. But somewhere along the way something changed. Mastering it meant discovering that it’s not such an impressive feat after all. Now that you can do it you see that there is a method to it, it’s not magic like you thought.

Could it be that the causality actually works in the opposite direction:  those skills that you eventually do master, you master them because you stop thinking of them as magic as start to think of them as routine methodical tricks.

Is it even possible for someone to be great at something and be in as much awe of himself as the rest of us failures are of him?

This guy wrote a column about The Hunger Games and gave away many details of the plot, some of them big-time spoilers.  Then he wrote a column about how he was actually doing his readers a favor because spoilers actually increase the enjoyment of the book.  For example

The suggestion is that there is a trade-off in the pleasures available to first-time readers or viewers on the one hand, and “repeaters” (as they are called in the scholarly literature) on the other. First-time readers or viewers, because they don’t know what’s going to happen, have access to the pleasures of suspense — going down the wrong path, guessing at the identity of the killer, wondering about the fate of the hero. Repeaters who do know what is going to happen cannot experience those pleasures, but they can recognize significances they missed the first time around, see ironies that emerge only in hindsight and savor the skill with which a plot is constructed. If suspense is taken away by certainty, certainty offers other compensations, and those compensations, rather than being undermined by a spoiler, require one.


The positive case for spoilers is even stronger if you are persuaded by those who argue, in the face of common sense, that suspense survives certainty. This is called “the paradox of suspense” and it is explained by A. R. Duckworth: “1. Suspense requires uncertainty. 2. Knowledge of the outcome of a narrative, scene or situation precludes any uncertainty. 3. [Yet] we feel suspense in response to fictions we know the outcomes of” (“The Paradox of Suspense II—The Problem,” The Journal of Film, Art and Aesthetics, Jan. 14, 2012).

and some other related arguments. Even if you accept these arguments, they amount to saying that there is a qualitative difference between the spoiled reading and the fresh reading and you want to have both. But this does not vindicate the spoilage. The problem with the spoiler is that it deprives you of the fresh reading. Spared the spoiler, or suitably alerted, you could have had both.

Now maybe you have time for only one reading. And so the counterargument could be that if the spoiled reading is in fact better than the fresh one then the spoiler saves you the effort of self-spoiling (settle down Beavis!) and gets you straight to the good, i.e. spoiled, stuff.

But notice what this says about the author of the novel. The author invented this whole story. She created the entire spoil-fodder. Indeed the spoiler only exists because the author chose not to “spoil” it himself by informing the reader right away what’s going to happen later. Either that is because this makes for a better story, or because the author is incompetent. In other words, putting a naked spoiler into your column and claiming that it makes the story better is tantamount to saying that the author is a hack. Not

If “The Hunger Games” is so shallow that it can be spoiled by a plot revelation, the alert doesn’t save much. If “The Hunger Games” is a serious accomplishment, no plot revelation can spoil it.

Deerstalker dash:  Alex Frankel.

Do memories depreciate slowly, bit by bit, or do they remain constant for some time and then wiped out completely?  For short term visual memory its the latter:

Which is exactly what happened: Zhang & Luck found that participants were either very precise, or they completely guessed; that is, they either remembered the square’s color with great accuracy, or forgot it completely. It was almost as if their memories behaved like files on a computer: Your Microsoft Word documents don’t lose letters over time, and your digital photos don’t yellow; rather, they continue to exist until you move them into the trash—where they are wiped out all at once.

But for long term memories its the former.  Check out this Scientific American article that surveys some recent research on the shelf life of memories.

Here’s a model of self-confidence. People meet you and they decide if they admire/respect/lust after you. You can tell if they do. When they do you learn that you are more admirable/respectable/attractive than you previously knew you were. Knowing this increases your expectation that the next person will react the same way. That means that when you meet the next person you are less nervous about how they will judge you. This is self-confidence.

Your self-confidence makes a visible impression on that next person. And it’s no accident that your self-confidence makes them admire/respect/lust after you more than they would if you were less self-confident. Because your self-confidence reveals that the last person felt the same way. When trying to figure out whether you are someone worthy of admiration respect or lust, it is valuable information to know how other people decided because people have similar tastes on those dimensions.

And of course it works in the opposite direction too. People who are judged negatively lose self-confidence and their unease is visible to others and makes a poor impression.

For this system to work well it must escape herding and prevent manipulation. Herding would be a problem if confident people ignore that others admire them only because they are confident and they allow these episodes to further fuel their confidence. I believe that the self-confidence mechanism is more sophisticated than this. Celebrities complain about being unable to have real relationships with regular people because regular people are unable to treat celebrities like regular people. A corollary of this is that a celebrity does not gain any more confidence from being mobbed by fans. A top-seeded tennis player doesn’t gain any further boost in confidence from a win over a low-ranked opponent who wilts on the court out of awe and intimidation.

Herding may be harder to avoid on the downside. If people who lack confidence are shunned they may never get the opportunity to prove themselves and escape the confidence trap.

And notwithstanding self-help books that teach you tricks to artificially boost your self-confidence, I don’t think manipulation is a problem either. Confidence is an entry, nothing more.  When you are confident people are more willing to get to know you better. But once they do they will learn whether your self-confidence is justified. If it isn’t you may be worse off than if you never had the entry in the first place.

Drawing:  Life is a Zen Roller Coaster from

Someone asks you a question and you have an intuitive understanding of precisely what is being asked. If you are not a game theorist you stop there and answer.

If you are a game theorist you start to analyze the question and discover that, as with all language there is some ambiguity. There’s more than one way to answer the question, the answer could be very detailed or just straightforward, the question might actually be rhetorical, there may be some implicit message to you in the question.

You begin to analyze how else she might have posed the same question. The fact that she chose this particular wording over another gives you clues about what precisely she is getting at. By a process of elimination this leads you to refine your interpretation of the question.

But if you are just a mediocre game theorist its pretty likely your analysis is totally wrong and you are worse off than if you hadn’t ever thought to analyze it. Indeed there is a good reason that your intuitive interpretation was the right one. Because the language evolved that way. And the evolution was probably so complex that there is no way a mediocre game theorist could have traced through the path of evolution to deduce that interpretation.

This is like how drugs can be found from compounds that have evolved in the plant and animal kingdom despite the fact that science has no way of knowing how to synthesize those.

And of course pretty much all of us are mediocre game theorists at best.

A rundown of various tricks restaurants use when arranging items on a menu. Including The Anchor, Siberia, Boxes and Bracketing.  A sampling:

4. In The Vicinity
The restaurant’s high-profit dishes tend to cluster near the anchor. Here, it’s more seafood at prices that seem comparatively modest.

5. Columns Are Killers

According to Brandon O’Dell, one of the consultants Poundstone quotes in Priceless,it’s a big mistake to list prices in a straight column. “Customers will go down and choose from the cheapest items,” he says. At least the Balthazar menu doesn’t use leader dots to connect the dish to the price; that draws the diner’s gaze right to the numbers. Consultant Gregg Rapp tells clients to “omit dollar signs, decimal points, and cents … It’s not that customers can’t check prices, but most will follow whatever subtle cues are provided.”

Montera move:  TYWKIWDBI

Check this out. Five numbers appear on a screen in different locations. They remain visible for 210 milliseconds and then they are obscured. The subject must then touch the locations in increasing order of the numbers that appeared there. That’s pretty much impossible. Here’s a human subject who is highly trained and does an impressive job but still fails miserably.


Now check out how nonchalantly this chimpanzee does it.


I didn’t even know they could count. Note that the 5 numbers are random integers between 1 and 9.  So the chimp is processing a binary relation in short-term memory, not to mention reading at a super-human rate. There are more videos here.  I saw these at Colin Camerer’s talk last week at Arthur Robson‘s conference on the Biological Basis of Preferences.

How much do your eyes betray you?

Have two subjects play matching pennies.  They will face each other but separated by a one-way mirror.  Only one subject will be able to see the other’s face.  He can only see the face, not anything below the chin.

Each subject selects his action by touching a screen.  Touch the screen to the West to play Heads, touch the screen on the East to play Tails.  (East-West rather than left-right so that my Tails screen is on the same side as your Tails screen.  This makes it easier to keep track.)

You have to touch a lighted region of the screen in order to have your move registered and the lighted region is moving around the screen.  This is going to require you to look at the screen you want to touch.  But you can look in one direction and then the other and touch only the screen you want.  Your hands are not visible to the other subject.

How much more money is earned by the player who can see the other’s eyes?

Now do the same with Monkeys.

(Conversation with Adriana Lleras-Muney)

Skip ahead to about 13:00.  It seems a little too neatly staged but it’s still hilarious.

Hardee heave:  Emil Temnyalov

Subjects video chat with each other. In one treatment subject A sees her own image in a small window in the corner of the chat, and in the other treatment (the control) there is no small window and she sees only the chat partner.

Subject B is not told about the two treatments and is simply asked to report how attractive subject A is. We want to know whether attractiveness is higher in the self-image treatment versus the control treatment.

This gets at a few different issues but the one I am curious about is this: do people know what it is about them that makes them attractive to others?

Also, we would want to track eye movements during the chat.

From The Chronicle of Higher Education

If you’re a psychologist, the news has to make you a little nervous—particularly if you’re a psychologist who published an article in 2008 in any of these three journals:Psychological Science, the Journal of Personality and Social Psychology,or the Journal of Experimental Psychology: Learning, Memory, and Cognition.

Because, if you did, someone is going to check your work. A group of researchers have already begun what they’ve dubbed the Reproducibility Project, which aims to replicate every study from those three journals for that one year. The project is part of Open Science Framework, a group interested in scientific values, and its stated mission is to “estimate the reproducibility of a sample of studies from the scientific literature.” This is a more polite way of saying “We want to see how much of what gets published turns out to be bunk.”

We should do this in economics.  But there is a less confrontational way to do it. Top departments in experimental economics attract PhD students who want hands on experience in the lab. These are departments like NYU and CalTech. They would benefit the profession, their students, and the reputation of their PhD programs, i.e. everybody concerned, if they were to add as a requirement that every student receiving a PhD must pick one recently published experimental article and attempt to replicate it.

Thanks to Josh Gans for the pointer.

From the Washington Post:

Funded by the U.S. Department of Health and Human Services, a panel of experts in psychology and economics, including Nobel laureate Daniel Kahneman, began convening in December to try to define reliable measures of “subjective well-being.” If successful, these could become official statistics.

Alan Krueger, Angus Deaton and Justin Wolfers have cameos in the article.

In Britain, Prime Minister David Cameron has embraced the idea, and last year the government began asking survey respondents things like “Overall, how happy did you feel yesterday?” and “Overall, how satisfied are you with your life nowadays?” The U.K. Economic and Social Research Council is also funding the U.S. panel’s $370,000 budget. In France, President Nicolas Sarkozy in 2008 launched a commission including two Nobel winners, Joseph Stiglitz and Amartya Sen, which opined that the “time is ripe for our measurement system to shift emphasis from measuring economic production to measuring people’s well-being.”

Far ahead in such measures, however, is the tiny Himalayan kingdom of Bhutan, which has embraced the notion of “Gross National Happiness” as a national goal and has created a commission to achieve it.

Sandeep wrote one of our most popular posts on this topic.  There was a survey that showed some correlation between pre-marital cohabitation and divorce.  Sandeep said its probably just a selection effect.

First, suppose one partner is reluctant to get married and has doubts about the relationship. More information would be helpful to decide whether to stay together or break up. If the couple cohabit, that will give them valuable information.  On the other hand, couples who are more confident about their relationship are more likely to get married straight away.  Hence, more stable couples are less likely to live together before marriage than less stable couples.  Living together per se is not the problem.  The real problem is that a deeper source of instability is correlated with cohabitation.

Second – and this theory is implicit in the research – more religious couples are less likely to get divorced and less likely to live together before marriage.  Again, selection explains the data and not cohabiting per se.

Now the Internet is back again with a new theory:  “sliding in.”

She was talking about what researchers call “sliding, not deciding.” Moving from dating to sleeping over to sleeping over a lot to cohabitation can be a gradual slope, one not marked by rings or ceremonies or sometimes even a conversation. Couples bypass talking about why they want to live together and what it will mean.

As in, no-sliding-in before marriage.  Because if you do, you might actually get locked in:

Sliding into cohabitation wouldn’t be a problem if sliding out were as easy. But it isn’t. Too often, young adults enter into what they imagine will be low-cost, low-risk living situations only to find themselves unable to get out months, even years, later. It’s like signing up for a credit card with 0 percent interest. At the end of 12 months when the interest goes up to 23 percent you feel stuck because your balance is too high to pay off. In fact, cohabitation can be exactly like that. In behavioral economics, it’s called consumer lock-in.

Does this make any sense?  Isn’t a couple who goes straight to the sliding in before getting married ultimately just as locked in as a couple who completely abstains from sliding in until they are locked in by the bonds of wedlock?

You are categorically opposed to some policy. She on the other hand is utilitarian and while she believes the policy is effective based on her current information she could be persuaded otherwise. You would like to persuade her if you could and in fact you have some information that might but it’s not guaranteed.

She opens the debate about the policy, states her arguments in favor and invites you to give any arguments against. But you are not interested in her information. You are categorically opposed to the policy and nothing would persuade you otherwise.

Moreover you are not even going to engage in the debate by trying to persuade her with your information. Because to do so would be to implicitly acknowledge that this is a debate that could be won by the side with the stronger argument.  That entails the risk that she and any observer might judge her arguments to be stronger and take an even firmer position in favor.

You are better off shutting down that front of the debate and insisting that it must be decided as a matter of principle, not utilitarianism.

I heard this story on NPR yesterday.

At some point, you likely received a present from a prepaid gift card from the person who wasn’t exactly sure what you’d want. Residents of New Jersey may not be able to buy them for much longer. American Express has pulled its gift cards from the state, and other big industry players are threatening to do the same. They oppose a new law that would allow New Jersey to claim unused gift card balances after two years. NPR’s Joel Rose reports.

As you may know, huge sums of money are loaded onto gift cards that are never redeemed.  The gift card “industry” leverages a wedge between your overly optimistic belief that you will not lose your gift card and the vendor’s knowledge that with quite high probability you will.  Is it welfare improving to prevent the vendor from profiting from this wedge?  Whatever welfare theory you are basing your conclusion on, it is not revealed preference, so what is it?  (Never mind that it’s the greedy government essentially trying to capture the same wedge.  Let’s assume for the sake of argument the unspent balance was automatically remitted to the purchaser of the card.)

Why doesn’t market competition already erode these profits?  (“Try our gift cards instead.  You will get any unpaid balance back, indeed with interest.”)

Related question.  Peet’s coffee has shrunk the size of their gift cards so that they are even easier to lose.  They do give you the choice whether you want a large gift card or a small one.  Are they being nice?

Twitter has finally acknowledged a long-suspected bug that makes users automatically unfollow accounts for no apparent reason, and now that it’s working on a fix, many would rather keep the bug to cover the awkwardness of manually unfollowing people. Time to admit you’re just sick of your friends’ updates, folks.

Of course, Twitter power users like Reuters’ Anthony De Rosa don’t really want to automatically lose followers, but it’s sort of funny for him to tweet “one benefit of the unfollow bug is it gives me an excuse if someone gets upset i unfollowed them.” De Rosa’s far from the only one. It seems likehundreds reacted with the same sentiment on hearing the news. That’s because it’s true that sometimes you keep following some idiot just because you don’t want the drama of dropping them. Look at how many people publiclycomplain about losing a follower. Well, tweeters, it’s time for us to take responsibility for our actions just a little bit more. Take a cue from The Awl’s Choire Sicha and embrace the hate.

The link came from Courtney Conklin Knapp, who I believe still follows me but I can’t be sure.

In basketball the team benches are near the baskets on opposite sides of the half court line. The coaches roam their respective halves of the court shouting directions to their team.

As in other sports the teams switch sides at halftime but the benches stay where they were. That means that for half of the game the coaches are directing their defenses and for the other half they are directing their offenses.

If coaching helps then we should see more scoring in the half where the offenses are receiving direction.

This could easily be tested.

Here’s a simple model of the slippery slope.  You have to adopt a position on an issue and defend your position to yourself and your critics.  The spectrum of positions ranges from the left-most extreme to the right-most extreme and you have to decide whether to take one of these extreme positions or some moderate point in the interior.

Defending a moderate position is a delicate balancing act.  It’s a very special set of utility functions which attain their maximum right at that point, and you need to convince your critics that the right utility function happens to be one of those.  Any slight perturbation of a utility function in that set will push you to the left or right so your critics have an easy task.  And once you’ve lost the first battle your credibility is damaged.

The easiest positions to defend are the extreme ones.  At an extreme position you have a binding constraint.  To defend your extremist position it is enough to say that you are such an extremist that you would like to move even farther to the right if that were possible.  The set of utility functions that have an optimum somewhere to the right of the right boundary is a large set.  You can perturb such a utility function and the extremist position will still be optimal.

The same logic explains why a few special interior positions can be robust to the slippery slope.  Think of a kinked budget constraint.  A large set of utility functions achieve their optimum at a kink.

The case of drosophilia:

In the study, male fruit flies that had mated repeatedly for several days showed no preference for alcohol-spiked food. On the other hand, spurned males and those denied access to females strongly preferred food mixed with 15 percent alcohol. The researchers believed the alcohol may have satisfied the flies’ desire for physical reward.

Over the course of your life you have to decide your position on a number of philosophical/social/political issues. You are open-minded so you collect as much data as you can before forming an opinion. But you are human and you can only remember so many facts.

There will come a time when the data you have collected make a very strong case for one particular position on issue A, say the right-wing position. When that happens you are pretty sure that there is never going to be enough evidence to overturn your position.

That’s not because you are closed-minded. That’s because you are very open-minded and based on the weight of all the evidence you collected and processed as objectively as a person can do, you have concluded that its very likely that this is the right position on A. And the fact that this is very likely the right position on A does not just imply but is indeed equivalent to saying that you attach very low probability to the future occurrence of strong evidence in the other direction.

Now that means that there’s not much point in collecting any more information about A. And indeed there’s not much point in remembering the detailed information that led you to this conclusion. The only reason for doing that would be to weigh it against future evidence but we’ve already established that this is unlikely to make any difference.

So what you optimally, rationally, perfectly objectively do is allow yourself to forget everything you know about A including all the reasons that justify your strongly-held views on A and to just make an indelible mental note that “The right-wing position on A is the correct one no matter what anyone else says and no matter what evidence to the contrary should come along in the future.”

The reason this is the rational thing to do is that you have scarce memory space. By allowing those memories to fade away you free up storage space for information about issues B, C, and D which you are still carefully collecting information on, forming an objective opinion about, in preparation for eventually also adopting a well-informed dogmatic opinion about.

Here is an excellent rundown of some soul searching in the neuroscience community regarding statistical significance.  The standard method of analyzing brain scan data apparently involves something akin to data mining but the significance tests use standard single-hypothesis p-values.

One historical fudge was to keep to uncorrected thresholds, but instead of a threshold of p=0.05 (or 1 in 20) for each voxel, you use p=0.001 (or 1 in a 1000).  This is still in relatively common use today, but it has been shown, many times, to be an invalid attempt at solving the problem of just how many tests are run on each brain-scan. Poldrack himself recently highlighted this issue by showing a beautiful relationship between a brain region and some variable using this threshold, even though the variable was entirely made up. In a hilarious earlier version of the same point, Craig Bennett and colleagues fMRI scanned a dead salmon, with a task involving the detection of the emotional state of a series of photos of people. Using the same standard uncorrected threshold, they found two clusters of activation in the deceased fish’s nervous system, though, like the Poldrack simulation, proper corrected thresholds showed no such activations.

Biretta blast:  Marginal Revolution.

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