Washington, Oct 14 It is well documented that humans freak out by almost-but-not-quite-real depictions of themselves. This visual phenomenon experienced by humans is known as the 'uncanny valley.' Now, researchers at Princeton University have found that monkeys have the tendency to react in the similar way.

It is the first such finding in any animal other than human.

The uncanny valley, a phrase coined by a Japanese researcher nearly three decades ago, describes that disquieting feeling that occurs when viewers look at representations designed to be as human-like as possible - whether computer animations or androids - but somehow fall short.

In the study, researchers found that macaque monkeys also fall into the uncanny valley, exhibiting this reaction when looking at computer-generated images of monkeys that are close but less than perfect representations.

"Increased realism does not necessarily lead to increased acceptance," said Asif Ghazanfar, an assistant professor of psychology and the Princeton Neuroscience Institute, who led the research.

According to authors, the work is significant because it indicates that there is a biological basis for the uncanny valley and supports theories that propose that the brain mechanisms underlying the uncanny valley are evolutionary adaptations.

"These data demonstrate that the uncanny valley effect is not unique to humans and that evolutionary hypotheses regarding its origins are tenable," said Ghazanfar.

Realistic-looking robots and computer avatars often spur negative responses in humans. Princeton University scientists showed monkeys these computer-generated images of monkeys and saw a similar response.

They found that monkeys also are unsettled by images that are realistic but synthetic, a response known as the 'uncanny valley' effect.

The study appears in the October Oct. 12 edition of the Proceedings of the National Academy of Sciences. (ANI)