Seth's Blog

At Berkeley, Andrew Gelman and I taught a freshman seminar about left-handedness. Half the students were left-handed. We did two fascinating studies with them that found that left-handers tend to have left-handed friends. I kick myself for not publishing those results, which I bring up in conversation again and again.

After the class ended I got a call from a journalist who was writing an article about ridiculous classes. I told him the left-handedness class had value as a way of introducing methodological issues but all I cared about was that his article be accurate. He decided not to include our class in his examples.

Stephen Christman, who got his Ph.D. from Berkeley (and did quirky interesting stuff even as a graduate student), and two colleagues have now published a paper that is a considerable step forward in the understanding of handedness. They argue that what really matters is not direction of handedness but the consistency of it. The terms left-handed and right-handed hide a confounding. Right-handers almost all have very consistent handedness (they do everything with the right hand). In contrast, left-handers much more often have inconsistent handedness: they do some things with the left hand, some with the right. I am a good example. I write with my right hand, bat and throw left-handed, play tennis left-handed, ping-pong right-handed. In fact, I am right-wristed and left-armed. When something involves wrist movement (writing, ping-pong) I use my right hand. When something involves arm movement (batting, throwing a ball, tennis), I use my left hand. Right-handers are much more similar to each other than left-handers.

Christman and his co-authors point to two things: 1. When you can get enough subjects to unconfound the two variables, it turns out that consistency of handedness is what makes the difference. Consistent left-handers resemble consistent right-handers.  2. Consistency of handedness predicts many things. Inconsistent-handers are less authoritarian than consistent-handers. They show more of a placebo effect. They have better memory for paragraphs. And on and on — about 20 differences. It isn’t easy to say what all these differences have in common but maybe inconsistent-handers are more flexible in their beliefs. (Which would explain the friendship findings in our handedness class.)

I think about these differences as another example of how every economy needs diversity and our brains have been shaped to provide it, one idea underlying my theory of human evolution. Presidents of the United States are left-handed much more than the general population. For example, Obama is left-handed. The difference between Presidents and everyone else is overwhelming and must mean something. Yet left-handers die younger. I would say that in any group of people you need a certain fraction, not necessarily large, to be open-minded and realistic. That describes inconsistent-handers (who are usually left-handed). These people make good leaders because they will respond to changing conditions. People who are not open-minded make good followers. Just as important as realism is cooperation, ability to work together toward a common goal.

This fascinating blog post by Josh Mittledorf points out that antioxidants, once believed to reduce aging by reducing oxidative damage, have turned out to have the opposite effect. By reducing a hormetic effect, they make things worse. I’m a friend of Bruce Ames, one of main proponents of the free radical theory of aging. I’ve heard him talk about it a dozen times. The turning point — the beginning of the realization that this might be wrong — was this 1994 study, which found that beta-carotene, a potent antioxidant, increased mortality. Bruce did not have a good explanation for the counter-theoretical result. However, Mittledorf doesn’t mention an important fact which doesn’t fit his picture. Selenium, a potent antioxidant, also powerfully reduces cancer. Don’t stop taking selenium.

I also like this theoretical paper by Mittledorf  about why aging evolved (turning off certain genes reduces aging) and how its evolution — not easily explained by conventional evolutionary ideas — is part of a range of phenomena that the conventional ideas cannot explain. One reason, maybe the main reason, that aging is adaptive is very Jane Jacobsian: it makes the community more flexible. Less likely to repeat old ways of doing things.

Thanks to Ashish Mukarji.

Do the heads of eBay and Amazon know about the Chinese shopping site Taobao (like eBay without auctions)? If so, why don’t they imitate it? Maybe they can’t match its bigger selection (e.g., food, detergent) and better prices, but they could imitate the better seller feedback and instant communication (chat boxes) with sellers.

In my theory of human evolution I propose that we have ceremonies, rituals, and festivals (and associated holidays) because they caused trading that would otherwise not have taken place. Ceremonies and so forth increased the demand for certain goods — gifts and high-end clothes, for example. These goods are important economically far out of proportion to their volume or monetary value or daily use because they increase innovation. They help the most skilled artisans– the ones most likely to innovate — make a living.

The leaders of Taobao understand this function of festivals/holiday and have put it to use: They have created new festivals/holidays. The biggest is Double Eleven (November 11), which started five years ago. On Double Eleven, a large fraction of taobao merchants have discounts, big (50%) and small (5%). Sales have grown each year and this year reached about $3 billion, according to one site. According to a Chinese friend, the sales were about $10 billion. CyberMonday (about $1 billion in 2011) is far behind

I have never read about this function of ceremonies, festivals, etc., in any economics book or paper. Double Eleven shows their economic force. This neglect is an example of what I consider the biggest problem with modern economics: lack of attention to and lack of understanding of innovation.

• Olive oil and the Willat Effect. “You can read about great olive oils, and their vast superiority over bad oils, all you want. . . . But until you try first-rate olive oil for yourself – actually put the good stuff in your mouth, and compare that experience to the bad stuff you’ve eaten in the past – you won’t really get it. . . . . Once you taste fine olive oils and their low-class imitations [side by side], though, you start to care.”
• Petraeus Affair: The journalism of what we don’t know.
• Tucker Max on book publishing. Disruptive innovation for popular authors.
• Animal self-medication. Sick animals eat differently than healthy animals.

Thanks to Alex Blackwood.

During my last visit to New York I bought a new black tea. I started drinking it a few weeks ago. I brewed it various ways (different amounts of tea, different steeping times, etc.) but had a hard time telling which way was best. This morning I decided I would learn how to  brew it by making paired comparisons (two cups of tea made the same way at the same time except for one difference). The fascinating thing, as I’ve said, about these side-by-side comparisons is that they produce hedonic changes. They change how much you like this or that. I call this the Willat Effect after my friend Carl Willat who caused me to notice it.

This morning I made two cups of the new tea. The two cups were brewed the same except in one case I “rinsed” the tea before brewing. Rinsing means I poured a bit of hot water on it and quickly got rid of the hot water. Rinsing tea removes from the final product whatever is transferred from the tea to the hot water in the first few seconds. In China, rinsing tea is common; in the United States, very rare.

I tasted the two cups (rinsed and unrinsed) side by side. The rinsed tea tasted much better. The unrinsed tea had something weird about it. Ugh, I thought, I can’t drink this. I threw out the unrinsed tea. Over the previous few weeks, I had happily drunk the new tea unrinsed many times. Now I found it repulsive.

• Did Jules Hoffman deserve the 2011 Nobel Prize in Medicine/Physiology? “Jules again, in his very subtle manner, described the Toll story as a team-work. I sat there, nauseated.”
• Babies given antibiotics more likely to be obese at age 3. This is very likely cause and effect because it is well-established that giving livestock antibiotics makes them fat.
• Lynn Yaeger on collecting. “I’ll be trying to get to the bottom of the mystery of what makes otherwise sane people spend all their money on King George coffee mugs.”
• Cultured Food Life
• Pushcart kombucha
• Sky natto

Thanks to Adam Clemens.

I have wondered for a long time how to apply my ideas about human evolution to teaching. My theory of human evolution says that specialization and trading are central to human evolution and includes a mechanism that increases diversity of expertise. The more diverse the expertise of you and your trading partners, the more you gain from trading. If I make knives and you make knives, we will gain less from trading than if I make knives and you make baskets.

I also discovered — independently — that the more choice I gave my Berkeley students (junior and senior psychology majors) about what to learn, the more they learned. It was as if they had an internal drive to learn all sorts of different things and the more I allowed that motivation to push and guide them, the more they learned. To see big effects it wasn’t enough to merely give them a wide choice of term paper topics (as many college teachers do). I pushed them out into the “real” (off-campus) world (they couldn’t do a library project) and said learn whatever you want. In this situation they learned an enormous amount. The connection with my theory of evolution was obvious: something inside of them was pushing them to be diverse in what they learned. What they learn = what they will become expert in. What they become expert in = what they will have to trade.

The more I allowed the underlying diversity of my students to be expressed, the more they learned. Yet almost all college classes treat all of the students in the class the same: same material, same assignments, same tests. The diversity of the students — especially the ways they differ from the professor — is a nuisance. So my theory suggests that standard college teaching is greatly at odds with human nature. It assumes one size fits all when that could hardly be more wrong.  It should be possible to greatly increase how much is learned by doing a better job of recognizing human nature. My experience so far supports this prediction.

Recently I thought of a new way to deal with diversity among my students. Next semester I will try it. One of the courses I am teaching (at Tsinghua University) is Frontiers of Psychology, with about 25 students. It’s required of freshman psychology majors. Here’s what I’ll do. For the first four or five class periods (one class per week), I’ll cover a wide range of psychological topics, ideas, and methods. There will be reading assignments (e.g., choose one paper out of 30 and do a class presentation) but no grading. Then every student will draw up a list of “learning goals” for the rest of the semester.  The goals can be whatever they want (related to psychology). They can read a book, read some articles, collect some data, give a talk to a high school class, whatever. Each goal will have a deadline. The assessment will be binary: goal completed/not completed. Their final grade will depend on how many goals they completed. The goals will be ordered. The further down their list they get, the higher their grade, with each level of completion assigned a grade at the beginning. They will make class presentations throughout the semester about their progress: what they are doing, what they have learned.

For the students, the benefits (compared to conventional teaching) are that (a) they get to learn exactly what they want yet (b) the grading criteria are very clear and (c) they are still motivated to work. For me, the benefits are that it should be a lot easier to judge if a goal has been completed than to grade homework essays, which is what I’ve done recently. Nor will I have to worry about what happens in class each week.

Any comments?

A new BBC series Metalworks! is about the history of British metal working. My theory of human evolution says that decoration — more precisely, our enjoyment of it — evolved because it helped the most skilled craftsmen make a living. Long ago, technology evolved via massive amounts of trial and error, which required subsidy since payoff (discovery with practical value) was so infrequent. It was much easier to discover/learn how to make something that looked better than something that worked better, but the two sorts of discoveries were correlated: trial and error produces both.

The episode on ironwork (The Blacksmith’s Tale) makes explicit how desire for decoration made it easier for the most skilled iron workers to make a living:

[Expert, at 16:50:] “I think decoration entirely depends on the amount of money the patron wanted to spend on that particular object.” [Narrator:] By the end of the 15th Century, wealthy patrons, such as the Church and monarchy, were hand-picking known craftsmen at the top of their game to match a commission’s requirements. When King Edward IV commissioned the Cornish smith John Tresillion to make these Gothic gates at Windsor in 1497, he did so with good reason. . . . [Expert:] “No blacksmith, ordinary blacksmith who was used to making horseshoes, could dream of working to this standard of perfection.”

Quality of decoration is easy to see. It doesn’t matter but it correlates with something that does matter — amount of trial and error (more trial and error, more innovation). We reward decoration to increase innovation.

The Shangri-La Diet derives from a theory of weight control that emphasizes smell-calorie learning. Smell-calorie learning evolved for the same logical reason. Smells don’t actually matter for health. But they are easy to notice and they correlate with things that do matter for health, such as calories. Via smell-calorie learning we learn the correlations. After that the foods that smell best are the ones that contain more calories.

In a recent post I proposed that we touch our mouths so much to transfer germs from our hands to our immune system. It’s an early warning system. The full sequence is: 1. Hands. 2. Skin around mouth. 3. Tongue (lick lips). 4. Tonsils (immune system). Forewarned is forearmed: exposure to a tiny amount of Germ X makes you much more likely to survive exposure to a large amount of Germ X.

Ants have a similar early-warning system, says a new study described here.

Cremer and her colleagues began by investigating how nestmates encountering an infected ant acted. They infected Lasius neglectus ants with Metarhizium anisopliae, a fungus that sticks to the insects’ outer cuticles and causes infection only after it has worked its way into the body, which takes a day or more. The researchers then placed infected or non-infected ants in a box with five nestmates, and watched what happened. . . .  Ants without the spores were groomed at a constant rate over 5 days, while Cremer saw a spike in grooming of the fungus-infected ants in the first day or two of infection, suggesting that the pathogen was prompting a behavior change in the nestmates.

The grooming was protective:

But even though they’d been exposed, only 2 percent of nestmates died from fungal infections, even though half of the initially infected ants, which had been dipped in solvent with M. anisopliae spores, died within 5 days. When ants were exposed to a dose of fungus expected to cause a 2 percent death rate, Cremer’s group saw an increase in antifungal activity, suggesting that this low level of infection was indeed enough to stimulate a protective immune response.

Earlier studies had shown what is called “social immunization” (“a protection of naive individuals of a colony after social contact to exposed individuals”) among insects. This study was about how social immunization happens.

After I thought of this explanation of mouth touching, I became much less concerned about contact with sick people. I hadn’t known about social immunization.

Carl Willat, for whom the Willat Effect is named, wrote to me:

I had two cartons of half and half in the fridge, neither had reached its expiration date but one was three days newer. I wondered if I could taste the difference between them, and I found that I could. Neither was sour, but one tasted fresher. I made a batch of vanilla ice cream out of each of them, figuring that together with the other ingredients I was adding (vanilla, egg yolks, cream, salt and sugar) the difference in taste would be less noticeable. After putting both mixtures through the ice cream freezer I tasted them [side by side] and one tasted a lot better. I gave a friend of mine a spoonful of each and she immediately noticed the difference. She correctly identified the good one and described it as tasting fresher and lighter. I can’t bear to eat the less good batch and I don’t know what to do with it. I don’t want to give it away for fear someone will think it representative of what my ice cream tastes like. I’m sure in the past I’ve made plenty of ice cream of this same quality that I and everyone else thought was perfectly acceptable, even delicious.

The fascinating part is “can’t bear to eat the less good batch”. Same thing with me and tea: In the last half year or so, I’ve made hundreds of side-by-side comparisons of tea. I now throw away cups of tea I don’t like. I never used to do that.