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Dreadful research, The early bird catches the caterpillar, Fixing air 250 years ago

by Michael Freemantle
June 19, 2006 | A version of this story appeared in Volume 84, Issue 25

Dreadful research

Would you prefer to wait for a mild electric shock or avoid the waiting by receiving a more intense shock now? It turns out that some people are prepared to opt for a higher voltage shock if they can get the shocking experience over and done with quickly. These people are categorized as "extreme dreaders" by a research team at Emory University School of Medicine, Atlanta, led by Gregory S. Berns. "Mild dreaders," on the other hand, prefer to be shocked as soon as possible but not if it means taking more voltage to do so.

The Emory team reached these dreadful conclusions following a study that employed a brain-imaging technique, known as functional magnetic resonance imaging, to examine the link between neural activity and the impact of the dread of future decisions having unpleasant outcomes (Science 2006, 312, 754). The experiments involved delivering electric shocks to the left feet of 30 or so courageous individuals. The researchers found that regions of the brain that are activated by pain are also activated by the anticipation of pain. Extreme dreaders could be distinguished from mild dreaders by the rate of increase of neural activity in these regions.

"It seems likely that an individual's relative preference for waiting for something unpleasant derives from previous experience," the authors say. They add that the neurobiological mechanisms governing dreading behavior may hold clues for both better pain management and improvements in public health.

Pied Flycatcher
Credit: Courtesy of Christiaan Both
Here's looking at you, chick.
Credit: Courtesy of Christiaan Both
Here's looking at you, chick.

The early bird catches the caterpillar

The blue tit, one of the most common birds in British gardens, parks, and woodlands, loves to feast on caterpillars because they are a nutritious and energy-rich source of food. Blue tit chicks alone may eat a phenomenal 150 billion caterpillars in the U.K. each year, according to the summer 2006 edition of the British magazine Birds, published by the Royal Society for the Protection of Birds. The chicks find small caterpillars especially tasty but, like many other birds, avoid the large hairy ones.

Caterpillars have a season and, because of human-induced climate change, it is getting earlier—at least in some areas of the Netherlands studied by a team of ecologists led by Christiaan Both at the University of Groningen. As trees advance their bud burst and plants advance their flowering times, the peak abundance of caterpillars occurs earlier. The caterpillar season also shortens because caterpillars grow faster and therefore pupate earlier at higher temperatures, the team notes.

An early caterpillar season may not be a problem for resident birds, such as blue tits, who can advance their laying dates, but it can be a problem for migratory birds who arrive too late to take advantage of the peak in caterpillar availability.

Last month, Both and colleagues reported the study of the impact of food peaks on nine Dutch populations of the pied flycatcher, a migratory songbird that flies to Europe after wintering in West Africa (Nature 2006, 441, 81). Caterpillars, they note, are an important food source for nestling flycatchers. They found that pied flycatcher populations in areas with early food peaks have declined by about 90% over the past two decades. In areas with late food peaks, the decline is small.

The group suggests that the general decline in many long-distance migratory species in both Europe and North America may be exacerbated by climate change because it exaggerates the mismatch between the seasonal habitats of the birds and their prey.

Fixing air 250 years ago

In 1756, Scottish scientist Joseph Black (1728-99) published a paper describing "experiments upon magnesia, quicklime, and other alkaline substances." The paper established the importance of quantitative experiments in chemistry. Black showed that carbonates lose CO2—which he called "fixed air"—when heated. He also showed that fixed air, unlike ordinary air, does not support combustion and turns limewater milky. In other experiments, he showed that fixed air is produced by burning charcoal, by fermentation, and by respiration.


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