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5 December 2013 11:26 am ,
Vol. 342 ,
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...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
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...
- 5 December 2013 11:26 am , Vol. 342 , #6163
- About Us
26 June 2001 7:00 pm
Even if you can't name one of Newton's laws, your inner physicist is a whiz at applying them to the real world. New research conducted aboard the space shuttle shows that the brain is quite sophisticated about predicting when a falling object will hit the ground, taking into account not just its position and speed, but even the tug of gravity.
Accurately guessing when an approaching object will hit you is an important survival skill. But researchers are still in the dark about how the brain translates visual images--for instance, a car becoming larger as it gets nearer--into an accurate representation of reality. Since the 1940s, researchers have preferred to explain perception by external cues only, such as the object's apparent size and position. But many in the field are starting to favor a different idea: that the brain develops a model of the physical world, which we use to predict the actions of objects around us. Such a model could include, for instance, acceleration due to gravity.
To study whether the brain can take gravity into account, Neuroscientist Joseph McIntyre of the European Laboratory for the Neuroscience of Action in Paris and Rome took advantage of a rare opportunity to take it away entirely. McIntyre and his colleagues gave four astronauts aboard the Neurolab space shuttle mission three tries to catch a falling ball, released at a different speed each time. On Earth, gravity would speed up the ball's descent, but in space, the balls fell at a constant velocity. When McIntyre measured the upward rotation of the forearm and stiffening of the biceps just before the subjects expected to catch the ball, he discovered that the catchers reacted early. Their failure to compensate for the lack of acceleration suggests that an internal model of gravity, rather than pure observation, shaped their perception of the falling object's behavior, McIntyre reports in the July issue of Nature Neuroscience. But the model seems adaptable, McIntyre says: After 15 days in space, the subjects' motor reaction matched the ball's impact more closely.
Although the internal model of gravity has been proposed before, it's never been tested directly until now, says perceptual motor psychologist James Tresilian of the University of Queensland, Australia, who calls the Neurolab experiments "quite an interesting way of going about it." As a proponent of the internal model theory, Tresilian is not surprised by the outcome. "It's what I would have expected," he says.