Exercising self-control is tough enough, but according to psychology professor Joshua Ackerman, the simple act of watching -- even imagining -- another person trying to exert self-control can exhaust the viewer's own capacity for restraint. Ackerman and colleagues report in the March issue of Psychological Science on experiments demonstrating this "vicarious depletion" effect.


Knowing that butterflies' wing markings can both frighten predators and attract mates, Darwin theorized that the markings on the lower surface evolved to frighten and the markings on top to attract. Jeffrey Oliver, a postdoctoral researcher in ecology and evolutionary biology, and colleagues have now confirmed that he was probably right. Their analysis of Bicyclus butterfly specimens showed the lower and upper surface markings evolved at different rates -- a sign they were responding to different evolutionary pressures. The work appeared online on April 1 in the Proceedings of the Royal Society B.


The most credible climate models show that in 30 years, the Arctic will be ice-free in summer. But according to Yale ice physicist John Wettlaufer and Caltech's Ian Eisenman, there won't be a catastrophic tipping point in this process because of a feedback loop that lets winter ice grow back faster when summer ice has thinned. The work appeared in the January 6 issue of the Proceedings of the National Academy of Sciences.


The use of another creature's cast-off shell for portable housing may greatly predate the hermit crab. For a study in the April Geology, geologist Adolf Seilacher and Amherst paleontologist James Hagadorn analyzed 500-million-year-old fossilized tracks. They found that the first arthropods to colonize the land carried shells from other animals, probably for protection from the elements.  

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