All animals may be born with an innate ability to recognize the movements of living things, according to a new study. This skill could be useful for everything from predator avoidance to helping young creatures find their mothers.
People have an easy time spotting the movements of animals. It's no sweat even in the lab, when the patterns are distilled down to just a few animated dots against a black background. More surprisingly, subjects can often tell the gender and emotional state of an abstract human figure simply by its movements. Because we can discern so much from such sparse information, scientists think specialized neural circuitry is at work. But it's not clear whether the ability is innate or learned.
In the new study, neuroscientist Giorgio Vallortigara of the University of Trieste in Italy and colleagues took newly hatched chicks and gave them a choice between two computer screens--one that showed dotted animation of a hen walking, and one that showed either a dotted hen shape rotating around an axis or dots moving at random. The chicks preferred to move towards the walking hen in 60% of the trials, the researchers report in the July issue of PLoS Biology. They even preferred biological motion when the dots were shifted so that the walking motion was still apparent, but the figure no longer resembled a hen.
Vallortigara says this shows that chicks are born with the ability to distinguish biological motion. Although no one has shown that human newborns have the same ability, Vallortigara says that's the implication of his research with chickens. The skill could be important for cognitive development in infants, he notes, encouraging them to focus on other people.
Marina Pavlova, an experimental psychologist at the University of Tuebingen in Germany, says the work is important because the chicks had never been exposed to light before they saw the animations, and therefore couldn't have learned to detect the motion. Showing the same innate talent in humans is difficult, she says, because even very young infants already have visual experience.