Darwin never warned against crossing black cats, walking under ladders or stepping on cracks in the pavement, but his theory of natural selection explains why people believe in such nonsense.

The tendency to falsely link cause to effect – a superstition – is occasionally beneficial, says Kevin Foster, an evolutionary biologist at Harvard University.

For instance, a prehistoric human might associate rustling grass with the approach of a predator and hide. Most of the time, the wind will have caused the sound, but “if a group of lions is coming there’s a huge benefit to not being around,” Foster says.

Foster and colleague Hanna Kokko, of the University of Helsinki, Finland, sought to determine exactly when such potentially false connections pay off.
Simplified behaviour

Rather than author just-so stories for every possible superstition – from lucky rabbit’s feet to Mayan numerology – Foster and Kokko worked with mathematical language and a simple definition for superstition that includes animals and even bacteria.

The pair modelled the situations in which superstition is adaptive. As long as the cost of believing a superstition is less than the cost of missing a real association, superstitious beliefs will be favoured.

Read the full article.

Years ago, my father told me of an industrial accident he had witnessed. Someone had climbed into a reaction chamber for routine inspection during a plant shutdown, when, unknown to him, a hidden hand opened a valve which flooded the chamber with nitrogen. He collapsed after a few minutes, unconscious. Another person climbed in to see what was wrong, tried to revive the unconscious engineer and himself collapsed. Both died for lack of oxygen soon after.

I remember being extremely surprised and somewhat skeptical – surely they would have felt the same rising panic we feel when holding our breath? There would be enough time and strength left over for a mad dash to the exit, even if it involved a climb… something didn’t add up.

Recently, I heard of a few more such accidents, and remembering the old story, dug around a bit. Turns out that the urge to breathe – air hunger – is triggered, not by low blood oxygen levels, but high carbon dioxide levels! Wikipedia continues: In mammals (with the notable exception of seals and some burrowing mammals), the breathing reflex is triggered by excess of carbon dioxide rather than lack of oxygen, so asphyxiation progresses in oxygen-deprived environments, such as storage vessels purged with nitrogen or helium balloons, without the victim experiencing air hunger. There are other interesting links about using nitrogen asphyxiation as a painless, humane method of killing animals including humans.

He points out that this is such pathetic design that the entire Intelligent Design argument falls flat on its face. Not that it will matter to the creationists, as can be seen from the following flowchart (click on image for full-size):

But, by now you should know that if there is one thing I enjoy, it is to take a poetic concept and kill it by introducing the prosody of science.

Anyway, the smell is called geosmin. And, in the spirit of scientific enquiry, here are the gory details, from howstuffworks.com:

As it turns out, the smells people associate with rainstorms can be caused by a number of things. One of the more pleasant rain smells, the one we often notice in the woods, is actually caused by bacteria! Actinomycetes, a type of filamentous bacteria, grow in soil when conditions are damp and warm. When the soil dries out, the bacteria produces spores in the soil. The wetness and force of rainfall kick these tiny spores up into the air where the moisture after a rain acts as an aerosol (just like an aerosol air freshener). The moist air easily carries the spores to us so we breathe them in. These spores have a distinctive, earthy smell we often associate with rainfall. The bacteria is extremely common and can be found in areas all over the world, which accounts for the universality of this sweet “after-the-rain” smell. Since the bacteria thrives in moist soil but releases the spores once the soil dries out, the smell is most acute after a rain that follows a dry spell, although you’ll notice it to some degree after most rainstorms.

Click here. From BBC. Go here for a lot more educational goodies.

White created the transparent fish, which he nicknamed Casper, by mating two existing zebrafish breeds, one that lacked a reflective skin pigment and the other without black pigment. The offspring had only yellow skin pigment, essentially appearing clear.

In one experiment, White and his colleagues inserted a fluorescent melanoma tumor into the abdominal cavity of the transparent fish. By observing the fish under a microscope, they found that the cancer cells started spreading within five days. White could actually see individual cells spreading.

See full article. They also have a picture of the fish for you to ogle.

In the first experiment, Li asked participants to act as “photo editors of a magazine” and choose among either appetite stimulating pictures of food or non-appetite stimulating pictures of nature. A control group was shown no pictures at all. All were then asked to participate in a lottery that would either pay them less money sooner or more money later.

Those who had been exposed to the photos of food were almost twenty percentage points more likely to choose the lottery with the chance of a smaller, more immediate payoff than those who were exposed to the photos of nature (61 percent vs. 41.5 percent) and eleven percentage points more likely to choose the short-term gain than those who had not been exposed to any stimulus (61 percent vs. 50 percent).

Similarly, another experiment used a cookie-scented candle to further gauge whether appetitive stimulus affects consumer behavior. Female study participants in a room with a hidden chocolate-chip cookie scented candle were much more likely to make an unplanned purchase of a new sweater — even when told they were on a tight budget — than those randomly assigned to a room with a hidden unscented candle (67 percent vs. 17 percent).

See full article (via boingboing).

In this study, she decided to look at whether our perception of how much exercise we are getting has any effect on how our bodies actually look. To do this, she studied hotel maids.

As any casual observer of the hospitality industry knows, hotel maids spend the majority of their days lugging heavy equipment around endless hallways. Basically, almost every moment of their working lives is spent engaged in some kind of physical activity.

Well, turns out that the maids don’t really think of their jobs are exercise. That is not good.

Despite the fact all of the women in her study far exceeded the U.S. surgeon general’s recommendation for daily exercise, the bodies of the women did not seem to benefit from their activity.

Langer and her team measured the maids’ body fat, waist-to-hip ratio, blood pressure, weight and body mass index. They found that all of these indicators matched the maids’ perceived amount of exercise, rather than their actual amount of exercise.

If you have been paying attention, you’ll notice that this is opposite of what we really wanted at the top of this page. Let’s see if something can be done about that.

So Langer set about changing perceptions.

She divided 84 maids into two groups. With one group, researchers carefully went through each of the tasks they did each day, explaining how many calories those tasks burned. They were informed that the activity already met the surgeon general’s definition of an active lifestyle.

The other group was given no information at all.

One month later, Langer and her team returned to take physical measurements of the women and were surprised by what they found. In the group that had been educated, there was a decrease in their systolic blood pressure, weight, and waist-to-hip ratio — and a 10 percent drop in blood pressure.

One possible explanation is that the process of learning about the amount of exercise they were already getting somehow changed the maids’ behavior. But Langer says that her team surveyed both the women and their managers and found no indication that the maids had altered their routines in any way. She believes that the change can be explained only by the change in the women’s mindset.

Essentially, what Langer is talking about is a placebo effect. She says that if you believe you are exercising, your body may respond as if it is.

Yippie! Read the full article while I go off and imagine that I am running the marathon.

I’d like to wish you a happy New Year, but I’m afraid I have a different sort of prediction.

You’re in for very bad weather. In 2008, your television will bring you image after frightening image of natural havoc linked to global warming. You will be told that such bizarre weather must be a sign of dangerous climate change — and that these images are a mere preview of what’s in store unless we act quickly to cool the planet.

Unfortunately, I can’t be more specific. I don’t know if disaster will come by flood or drought, hurricane or blizzard, fire or ice. Nor do I have any idea how much the planet will warm this year or what that means for your local forecast. Long-term climate models cannot explain short-term weather.

But there’s bound to be some weird weather somewhere, and we will react like the sailors in the Book of Jonah. When a storm hit their ship, they didn’t ascribe it to a seasonal weather pattern. They quickly identified the cause (Jonah’s sinfulness) and agreed to an appropriate policy response (throw Jonah overboard).

[...]When judging risks, we often go wrong by using what’s called the availability heuristic: we gauge a danger according to how many examples of it are readily available in our minds. Thus we overestimate the odds of dying in a terrorist attack or a plane crash because we’ve seen such dramatic deaths so often on television; we underestimate the risks of dying from a stroke because we don’t have so many vivid images readily available.

Slow warming doesn’t make for memorable images on television or in people’s minds, so activists, journalists and scientists have looked to hurricanes, wild fires and starving polar bears instead. They have used these images to start an “availability cascade,” a term coined by Timur Kuran, professor of economics and political science at Duke University, and Cass R. Sunstein, a law professor at the University of Chicago.

The availability cascade is a self-perpetuating process: the more attention a danger gets, the more worried people become, leading to more news coverage and more fear. Once the images of Sept. 11 made terrorism seem a major threat, the press and the police lavished attention on potential new attacks and supposed plots. After Three Mile Island and “The China Syndrome,” minor malfunctions at nuclear power plants suddenly became newsworthy.

See full article. If you want to get confused about global warming, it might be a good idea to see Al Gore’s An Inconvenient Truth, and then go read Michael Crichton’s State of Fear. That should convince you to stop getting involved in weighty issues like this and go back to Rakhi Sawant’s antics.

See also my earlier post on global dimming.

By the way, Al Gore’s movie is an excellent example of how to give a good Powerpoint presentation – as opposed to the bullet-point ridden junk that you usually turn out. (Essentially the entire movie is a Nobel-prize winning slide show presented by Al Gore.)

Michael Wesch, who teaches cultural anthropology at Kansas State University, spent two years living with a tribe in Papua New Guinea, studying how people forge social relationships in a purely oral culture. Now he applies the same ethnographic research methods to the rites and rituals of Facebook users.

“In tribal cultures, your identity is completely wrapped up in the question of how people know you,” he says. “When you look at Facebook, you can see the same pattern at work: people projecting their identities by demonstrating their relationships to each other. You define yourself in terms of who your friends are.”

Read full article. Quite interesting.