July 2, 2009
What led to the birth of human civilization? How did a naked ape manage to invent complex cultural forms such as language and art? One possibility is that something happened inside the mind, that a cortical switch was flipped and homo sapiens was suddenly able to paint on cave walls. But that doesn't seem to be the case, as UCL anthropologist Ruth Mace explains in a recent Science article:
Traits such as the creation of abstract art, improvements in stone and other tools, long-distance "trading," and the manufacture of musical instruments mark the emergence of modern humans who behaved much as we do (see the figure). These material expressions of the modern condition emerged much later than did anatomically modern humans. Some aspects of behavioral modernity first appeared in southern Africa, possibly as early as 90,000 years ago, only to disappear again and reappear in Eurasia ~45,000 years ago. The timing of these events makes a biological change in cognitive capacity a somewhat unlikely explanation.
What, then, led to the birth of "modern human behavior"? A new paper by Adam Powell, et. al. argues that the crucial shift was increasing population density. The main evidence for this effect comes from genetic studies of the late Pleistocene, which demonstrate that "densities in early Upper Paleolithic Europe were similar to those in sub-Saharan Africa when modern behavior first appeared."
The larger implication is that the birth of human culture was triggered by a new kind of connectedness. For the first time, humans lived in dense clusters, and occasionally interacted with other clusters, which allowed their fragile innovations to persist and propagate. The end result was a positive feedback loop of new ideas.
While it's very nice to have some statistical evidence for this idea (even if I can't pretend to understand the "Bayesian coalescent inference" method used by the scientists to calculate the population densities in the late Pleistocene), it's worth pointing out that the density explanation isn't particularly new. In The Economy of Cities, Jane Jacobs forcefully argued against the "dogma of agricultural primacy," which assumed that farmers and agricultural innovations made civilization possible. Jacobs argued that the dogma was exactly backwards, and that it was the density of urbanesque clusters which generated the innovations that made farming possible. As Jacobs writes: "It was not agriculture then, for all its importance, that was the salient invention...Rather it was the fact of sustained, interdependent, creative city economies that made possible many new kinds of work." After all, you can't learn how to grow food until you've got a system for transmitting knowledge, which is why population density is so essential.
Posted by Jonah Lehrer at 11:57 AM • 5 Comments • 0 TrackBacks
July 1, 2009
In the latest issue of In Character, UPenn psychologist Angela Duckworth criticizes the systematic attempt to improve self-esteem in children:
Q: Educators for some time now have put a premium on self-esteem. Schools strive to help kids develop self-esteem on the theory that other good things such as achievement will flow from increased self-esteem. Which is more important, self-discipline or self-esteem, for being successful as a student?
DUCKWORTH: Ah, how great to be asked this question! We did a study in which we followed kids for four years. We took their self-control ratings from parents and teachers and the kids themselves. We tracked them every year, and we kept their grades from school records, not from their own reports on their grades. We pitted self-control and self-esteem -- we also took measures for both -- against each other. Here's what we found: When kids increase in self-control, their grades go up later. But when kids increase their self-esteem, there is no effect on their grades. The bottom line is that our research shows that self-control is more important than self-esteem in determining achievement. People have been studying self-esteem for a long time, and this allows you to compare the self-esteem of kids who grew up in the nineties with, say, those who grew up in the seventies or eighties with regard to self-esteem. Self-esteem has gone up in the United States; achievement has not. If anything, compared with other countries, we have done worse, but our kids feel really good about themselves on average. What seems particularly interesting, and there is an article by J. P. Tangney on this, is that there is an uncoupling between your perception of your own competence and how much you like yourself. Many American kids, particularly in the last couple of decades, can feel really good about themselves without actually being good at anything. This is the problem with the "self-esteem at all costs" message. Self-esteem should be earned. I find that parents today, at least those in a high socioeconomic bracket, never want to say anything critical of their children. Everybody has to be a winner. You take your children to a soccer game, and they don't keep score anymore. They don't want anybody to lose. Well, it's a good thing for kids to lose sometimes. They see what it's like to get up again. They realize it's not the end of the world.
If you're looking for a comprehensive summary of why self-esteem doesn't predict success, check out this review article by Baumeister, et. al. Here's the takeaway:
Overall, the benefits of high self-esteem fall into two categories: enhanced initiative and pleasant feelings. We have not found evidence that boosting self-esteem (by therapeutic interventions or school programs) causes benefits. Our findings do not support continued widespread efforts to boost self-esteem in the hope that it will by itself foster improved outcomes. In view of the heterogeneity of high self-esteem, indiscriminate praise might just as easily promote narcissism, with its less desirable consequences.
Posted by Jonah Lehrer at 10:39 AM • 13 Comments • 0 TrackBacks
I've got a thing for things that are sweet and salty. Caramels with sea salt. French fries with plenty of ketchup. Peanut butter and strawberry jelly. Melon with prosciutto. Is there anything better to eat on a hot summer day than a ripe cantaloupe dressed with some cured meat, thinly sliced? I think not.
But why do sweet and salty sing so well together? Why do we add a pinch of salt to chocolate cake, or not fully taste the sweetness of a tomato until it's been sprinkled with sodium chloride? And why does bread without salt taste so bland?
The first thing to understand is how we perceive saltiness. It's an elegantly simple setup: sodium ion (Na+) channels are perched on the surface of the tongue. When sodium chloride enters the mouth, it dissolves in saliva and then directly alters the membrane potential of the taste cell. The end result is an influx of positively charged sodium ions, which depolarize the cell and trigger an action potential. The brain is told that we've tasted something salty.
Sweet is a more complicated taste sensation. It begins when a sweet tastant (glucose, fructose, sucralose, etc.) binds to a G-protein coupled receptor, which then triggers an enzymatic cascade. But the fast cellular process ends up in the same place, as the taste receptor cells start to depolarize. (That's a fancy way of saying they increase the amount of positive ions on the inside of their membrane. This accumulation of voltage is what allows them to pass on the electrical message to other neurons.)
But back to the salty-sweet conundrum. Why does melon and prosciutto taste so good? Although the sweet taste receptor seems to be a G-protein coupled receptor, there's also evidence that applying a sodium-channel blocker (TTX) can dramatically inhibit the activity of all taste receptors, suggesting that sodium plays a key role in the cellular detection of every taste (and not just the taste of salty things). While previous work has emphasized the role of potassium ions and calcium ions in the depolarization of sweet taste receptors, I wonder if sodium ions might also play a role. Perhaps, and this is a pretty big perhaps, the extra concentration of salt when added to a dark chocolate souffle or a caramel makes it easier for the sweet taste receptors to fire an action-potential, since there are more sodium ions floating around the apical membrane. This would also explain why food without any salt is so hopelessly boring: it might be literally harder for our various taste receptors to get excited. Just a thought.
The other alternative is that the amplification of sweet by salt occurs downstream, at some later stage of sensory processing. Who knows? All I know is that I'm having a watermelon and feta salad for lunch.
Posted by Jonah Lehrer at 7:33 AM • 7 Comments • 0 TrackBacks
June 30, 2009
It's been a hotly debated scientific question for decades: was Joe DiMaggio's 56-game hitting streak a genuine statistical outlier, or is it an expected statistical aberration, given the long history of major league baseball? I'd optimistically assumed, based on the work of Harvard physicist Ed Purcell (as cited by Stephen Jay Gould) that DiMaggio was the real deal. Here's Gould:
Purcell calculated that to make it likely (probability greater than 50 percent) that a run of even fifty games will occur once in the history of baseball up to now (and fifty-six is a lot more than fifty in this kind of league), baseball's rosters would have to include either four lifetime .400 batters or fifty-two lifetime .350 batters over careers of one thousand games. In actuality, only three men have lifetime batting averages in excess of .350, and no one is anywhere near .400 (Ty Cobb at .367, Rogers Hornsby at .358, and Shoeless Joe Jackson at .356). DiMaggio's streak is the most extraordinary thing that ever happened in American sports.
But science, with its relentless pursuit of fact and abhorrence of anomalies, has apparently concluded that DiMaggio wasn't so special after all. In their latest excellent podcast, Radiolab interviews Steve Strogatz, a mathematician at Cornell, who worked with his student Sam Arbesman to simulate the history of MLB only to demonstrate that there was nothing statistically freakish about DiMaggio's hitting streak. Others, however, aren't quite so sure. The controversy continues.
Posted by Jonah Lehrer at 8:19 AM • 2 Comments • 0 TrackBacks
Just a quick reminder to watch the season premiere of NOVA tonight on PBS. It features Oliver Sacks and a few of the patients described in Musicophilia, including Tony Cicoria, an orthopedic surgeon who became obsessed with classical piano after being struck by lightning. I found the show quite compelling - NOVA was kind enough to send me a preview DVD - so be sure to tune in. For me, the most affecting story was that of Matt Giordano, who suffers from a severe case of Tourette's syndrome. Matt is hard to watch, if only because his ordinary movements are constantly being interrupted by tics and twitches. Fortunately, Matt has discovered a temporary cure for his Tourette's: drumming. When he's playing on the drums, the spasms disappear, and Matt is able to execute movement with an uncanny sense of timing.
Bonus video: Dr. Sacks on The Daily Show:
Posted by Jonah Lehrer at 6:55 AM • 5 Comments • 0 TrackBacks
June 29, 2009
In the latest Atlantic, Sandra Tsing Loh argues (with her usual panache) that the institution of marriage is passé, and that it's time to cast off the antiquated concept of eternal monogomy:
Sure, it [marriage] made sense to agrarian families before 1900, when to farm the land, one needed two spouses, grandparents, and a raft of children. But now that we have white-collar work and washing machines, and our life expectancy has shot from 47 to 77, isn't the idea of lifelong marriage obsolete?
This post isn't about whether Loh is right; I've only been married 9 months, so I'm not qualified to hold an opinion on whether or not the institution is hopelessly retrograde and really does, as Loh suggests, lead to sexless misery. But I did want to point out that the scientific evidence Loh trots out to defend her thesis (and it's really an unnecessary reference, since she's making a cultural argument, not a biological one) is bunk. She uncritically references the anthropologist Helen Fisher, and quotes her thusly:
Fisher, a women's cult figure and an anthropologist, has long argued that falling in love--and falling out of love--is part of our evolutionary biology and that humans are programmed not for lifelong monogamy, but for serial monogamy. (In stretches of four years, to be exact, approximately the time it takes to get one kid safely through infancy.)
Why Him? Why Her? explains the hormonal forces that trigger humans to be romantically attracted to some people and not to others (a phenomenon also documented in the animal world). Fisher posits that each of us gets dosed in the womb with different levels of hormones that impel us toward one of four basic personality types:
The Explorer--the libidinous, creative adventurer who acts "on the spur of the moment." Operative neurochemical: dopamine.
The Builder--the much calmer person who has "traditional values." The Builder also "would rather have loyal friends than interesting friends," enjoys routines, and places a high priority on taking care of his or her possessions. Operative neurotransmitter: serotonin.
The Director--the "analytical and logical" thinker who enjoys a good argument. The Director wants to discover all the features of his or her new camera or computer. Operative hormone: testosterone.
The Negotiator--the touchy-feely communicator who imagines "both wonderful and horrible things happening" to him- or herself. Operative hormone: estrogen, then oxytocin.
Fisher reviewed personality data from 39,913 members of Chemistry.com. Explorers made up 26 percent of the sample, Builders 28.6 percent, Directors 16.3 percent, Negotiators 29.1 percent. While Explorers tend to be attracted to Explorers, and Builders tend to be attracted to Builders, Directors are attracted to Negotiators, and vice versa.
She fails to note that Fisher is a paid consultant to Chemistry.com, a division of Match.com which uses these vague neurosciency profiles as a selling point. While Fisher has done some interesting work on romantic attachment in the past, it's worth pointing out that there's exactly zero evidence that people have "dominant" or "operative" neurotransmitter system, or that being exposed to oxytocin in the womb makes us touchy-feely. (There is evidence, however, that various polymorphisms for specific receptor subtypes, such as the DRD2 dopamine receptor, do correlate weakly with attachment style.) As Vaughan Bell smartly notes in a MindHacks critique of Fisher, his "dominant chemical is caffeine". This time of year, my dominant chemical would be ethyl alcohol, preferably in the form of a pale ale or rose wine.
Of course, such neurobabble is only the latest (pseudo)scientific evidence used to critique the institution of marriage. Before testosterone and dopamine, there was the Freudian id, followed by the misapplication of strong versions of evolutionary psychology. This doesn't mean that Loh is wrong; maybe marriage really deserved to die with the 19th century. But that's an argument about property rights, the legal system, childcare, etc. It has nothing to do with dopamine.
Posted by Jonah Lehrer at 4:57 PM • 17 Comments • 0 TrackBacks
June 26, 2009
If anybody happens to be in New Haven this evening, I'll be speaking about Proust, art, science, wine and Descartes with the psychologist Paul Bloom. It will be fun and it's free. The event starts at 5:30 and is at the Yale Center for British Art.
Posted by Jonah Lehrer at 7:21 AM • 1 Comments • 0 TrackBacks
June 25, 2009
It's a shame that we stop encouraging naps once the preschool years are over. After all, there's a growing body of scientific evidence that the afternoon siesta is an important mental tool, which enhances productivity, learning and memory. (It's really much more effective than a cup of coffee.) Here's the Times:
Have to solve a problem? Try taking a nap. But it has to be the right kind of nap -- one that includes rapid eye movement, or REM, sleep, the kind that includes dreams.
Researchers led by Sara C. Mednick, an assistant professor of psychiatry at the University of California, San Diego, gave 77 volunteers word-association tests under three before-and-after conditions: spending a day without a nap, napping without REM sleep and napping with REM sleep. Just spending the day away from the problem improved performance; people who stayed awake did a little better on the 5 p.m. session than they had done on the 9 a.m. test. Taking a nap without REM sleep also led to slightly better results. But a nap that included REM sleep resulted in nearly a 40 percent improvement over the pre-nap performance.
The study, published June 8 in The Proceedings of the National Academy of Sciences, found that those who had REM sleep took longer naps than those who napped without REM, but there was no correlation between total sleep time and improved performance. Only REM sleep helped.
Numerous studies have now demonstrated that REM sleep is an essential part of the learning process. Before you can know something, you have to dream about it.
This outlandish notion began with a scared rabbit. In the early 1950s, scientists at UCLA discovered that the rabbit hippocampus, when aroused by some fearful stimulus in its environment (a coyote, for example), would start pulsing with a very distinctive beat, which they dubbed the "theta rhythm." Subsequent studies found the same beat in several species, but only when the animals were extremely excited or scared or were engaged in an active motor movement. Rats exuded a theta rhythm whenever they were exploring their cage. Cats had it stalking prey. But what was this rhythm's function? Why did the hippocampus--a brain structure involved in learning and memory--become active in this way during moments of intense awareness? Stumped, the UCLA scientists shelved their work and moved on to other things.
Years later, Case H. Vanderwolf of the University of Western Ontario made an even stranger discovery: Theta rhythm was also present during sleep--activity and rest provoked the same strange brain activity. Nobody could figure out the meaning of this.
The breakthrough came in 1972, when psychologist Jonathan Winson came up with a simple theory: The rabbit brain exhibited the same pattern of activity when it was scared and when it was dreaming because it was dreaming about being scared. The theta rhythm of sleep was just the sound of the mind processing information, sorting through the day's experiences and looking for any new knowledge that might be important for future survival. They were learning while dreaming, solving problems in their sleep.
Winson's theory was ridiculed. At the time, most scientists assumed that our dreams were accidents of the brain stem, nothing more than a Dadaist montage of meaningless hallucinations. But Winson maintained that this hypothesis made no sense. For one thing, our dreams don't seem random. Instead, they unfold in intricate narrative scenarios, which tend to reflect our daily activities. According to Winson, these nighttime stories--that flurry of theta rhythm--were actually carefully scripted events, in which our new knowledge was put to the test. Did our new learning help us solve our invented problems? Was it a good "survival strategy?" If the answer was yes, then the knowledge was woven into the brain. We woke up a smarter person. The rabbit figured out how to escape its predator. We also, therefore, learn by pretending to do.
Whatever the elegance of Winson's theory, he lacked conclusive evidence. What he needed was a study that directly linked a brain's real-world experience with its manufactured dreams. That study arrived in 2001, when Matthew Wilson, a professor at MIT, published a paper in Neuron ("Temporally Structured Replay of Awake Hippocampal Ensemble Activity during Rapid Eye Movement Sleep") about the dreams of rats.
Wilson began his experiment by training rats to run through mazes. While a rat was running through one of these labyrinths, Wilson measured clusters of neurons in the hippocampus with multiple electrodes surgically implanted in its brain. As he'd hypothesized, Wilson found that each maze produced its own pattern of neural firing. To figure out how dreams relate to experience, Wilson recorded input from these same electrodes while the rats were sleeping. The results were astonishing. Of the 45 rat dreams recorded by Wilson, 20 contained an exact replica of the maze they had run earlier that day. The REM sleep was recapitulating experience, allowing the animals to consolidate memory and learn new things. Wilson's lab has since extended these results, demonstrating that "temporally structured replay" occurs in both the hippocampus and visual cortex.
Posted by Jonah Lehrer at 7:17 AM • 15 Comments • 0 TrackBacks
June 22, 2009
I went jean shopping this weekend. Actually, I went to the mall to return a t-shirt but ended buying a pair of expensive denim pants. What happened? I made the mistake of entering the fitting room. And then the endowment effect hijacked my brain. Let me explain.
The endowment effect is a well studied by-product of loss aversion, which is the fact that losing something hurts a disproportionate amount. (In other words, a loss hurts more than a gain feels good.) First diagnosed by Richard Thaler and Daniel Kahneman, the endowment effect stipulates that once people own something - they have an established or imagined "property right" to the object - that something dramatically increases in subjective value. Wikipedia has an excellent summary of an experiment documenting the endowment effect by Dan Ariely and Ziv Carmon:
Duke University has a very small basketball stadium and the number of available tickets is much smaller than the number of people who want them, so the university has developed a complicated selection process for these tickets that is now a tradition. Roughly one week before a game, fans begin pitching tents in the grass in front of the stadium. At random intervals a university official sounds an air-horn which requires that the fans check in with the basketball authority. Anyone who doesn't check in within five minutes is cut from the waiting list. At certain more important games, even those who remain on the list until the bitter end aren't guaranteed a ticket, only an entry in a raffle in which they may or may not receive a ticket. After a final four game, Carmon and Ariely called all the students on the list who had been in the raffle. Posing as ticket scalpers, they probed those who had not won a ticket for the highest amount they would pay to buy one and received an average answer of $170. When they probed the students who had won a ticket for the lowest amount they would sell, they received an average of about $2,400. This showed that students who had won the tickets placed a value on the same tickets roughly fourteen times as high as those who had not won the tickets.
What does this have to do with fitting rooms and jeans? Once I tried on the pants, I became an implicit owner of them. I stared at myself in the mirror and admired the fit, the wash, etc. I thought about how good they would look with my shoes. I contemplated wearing them to various upcoming events and all the strangers who would look at my pants and think "Those are nice pants!" In other words, I spent a few minutes imagining my life with these new jeans and, once that happened, the pants suddenly became much more valuable. I mentally endowed myself with the object and didn't want to lose something that I didn't even own. As a result, the ridiculous price tag ($170 for Levis!) no longer seemed so ridiculous. The lesson? Don't try something on that you don't want to buy.
Update: Via a reader (thanks Alon!) comes this study, which demonstrates that merely touching an item can trigger the endowment effect.
Posted by Jonah Lehrer at 7:29 AM • 15 Comments • 0 TrackBacks
