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5 December 2013 11:26 am ,
Vol. 342 ,
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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The Magpie in the Mirror
19 August 2008 (All day)
When Goldie the European magpie looked in the mirror and spotted a yellow dot on her black neck feathers, she did what we all do when we see a spot of mustard on our chins: She wiped it off. Her reaction to her image--apparently recognizing the bird in the mirror as herself--has scientists excited. It's the first time that mirror self-recognition (MSR) has been found in birds or in any nonmammalian species.
MSR is regarded as evidence of knowing who you are--a higher neural skill underlying human abilities such as self-consciousness and self-reflection. Researchers have given the MSR test to a wide variety of species. Most fail, typically perceiving the image as a rival and attacking it. Certain species of primates have passed the test, however, and recent experiments with dolphins and elephants suggest that they, too, have the ability (ScienceNOW, 30 October 2006). "That was the first indication that the skill is not limited to primates," says Helmut Prior, a cognitive psychologist at Goethe University in Frankfurt, Germany, and the lead author of the study. Elephants and dolphins belong to complex societies, he notes, so MSR may be present only in species for which empathy and social understanding are important.
Because corvids, the family of birds that includes magpies, ravens, and jays, are also highly social, Prior decided to test them, selecting magpies specifically because they are "very curious and observant." Prior and his team first placed five birds--one at a time--in a cage with two compartments, one of which contained a mirror. Three magpies spent most of their time in the section with the mirror, looking behind it, or moving back and forth in front of it--in essence, learning what it does. Then, the scientists affixed red, yellow, or black dots to the feathers beneath the magpies' beaks and placed the birds in cages with mirrors. Because the black dots closely matched the color of the birds' feathers, they served as a control for whether the birds merely felt the dots on their bodies.
As the researchers report today in PLoS Biology, two of the birds, Goldie and Gerti, spotted the dots on their reflections and tried to peck and scratch these off, suggesting that they passed the MSR test. If the birds were in mirrorless cages, they didn't touch the dots. Although only two birds seemed to show self-awareness, Prior says that this is similar to the success rate in chimpanzees.
The ancestors of birds and mammals separated 300 million years ago, so MSR in these two lineages must have evolved independently, says Prior, noting that similar social pressures probably cause it to emerge. "Most of the avian brain is completely different from the mammalian brain," he adds. Thus, the study shows that MSR "is not tied to a particular neural structure," such as the mammalian neocortex, as some researchers have argued, says Prior.
"The study is very compelling," says primatologist Frans de Waal of Emory University in Atlanta, Georgia. "[It's] in fact better controlled than anything we have on children, who after one touch to a sticker on their head are declared to have MSR." The work indicates that "MSR may be more widely distributed among species than previously thought," adds Diana Reiss, a cognitive psychologist at Columbia University who participated in the dolphin and elephant MSR tests. "You don't need a primate-type brain."