New York, April 17. (PTI): The new finding that animals and machines can engage in self-reflection are bound to shock humans and hurt their ego as it was until now thought that this is the quality which they exclusively possess, a study claimed.

It is called "metacognition" -- the ability to think, to engage in self-reflection, to introspect.

It was long thought to be not just something that we have more of or do better than machines or animals, but that we have and they lack.

But Newsweek reports that this barrier of exceptionalism too now is on the rocks as both animals and machines show signs that they can engage in self-reflection.

In the latest study, scientists tested for introspection in rats.

Jonathon Crystal and Allison Foote of the University of Georgia trained rats to push one lever when they heard a short burst of static, and a second lever when they heard a long burst.

The reward for a right answer was six food pellets. A wrong answer yielded nothing. But refusing to answer like a student fleeing an exam room upon seeing the impossible questions earned the rat a consolation prize of three morsels.

Clearly, the smart strategy was to respond if sure of the answer, but pass if not.

The rats got almost perfect scores when they had to identify two-second or eight-second bursts. But when they heard static of intermediate duration and had to choose "long" or "short," they were twice as likely to decline the test and take the three pellets; they knew what they didn't know.

To make sure the rats were truly introspecting, the scientists then eliminated the opt-out choice and required the rats to choose "long" or "short" for the medium bursts.

The animals got half right, no better than guessing, which suggests that when they opted out, it was indeed because they had assessed the contents of their mind "do I know this?" and made the rational choice, the scientists report in Current Biology.

"Rats can reflect on their internal mental states," says Crystal. "They know when they don't know." Other scientists have gotten similar results with dolphins and rhesus monkeys, who also decline to take a test when they don't know the answer. They think about thinking.

Some defenders of humanity's lock on consciousness, Newsweek says, have argued that a rat or monkey need not be self-aware to tell that it doesn't know something; ignorance might be expressed as "no test for me, thanks" unconsciousness.

Funny they should mention circuits, the magazine says and quotes Michael Cox of BBN Technologies as saying that after decades in which metacognition was written off by many researchers in artificial intelligence, it is getting serious attention.

"I don't think there is an inherent barrier to self-understanding on the part of machines," says Cox. "There is nothing magical, mystical, spiritual or uniquely human about introspection and metacognition."

Questions about consciousness, Newsweek says, have become especially poignant in the case of comatose patients.