New York, Dec 19 (IANS): The so called 'high order' abstract reasoning process thought to be limited till now only to humans and certain apes has now been discovered in crows.

Crows have the brain power to solve higher-order, relational-matching tasks and they can do so spontaneously, the findings showed.

The findings suggest that birds are much smarter than previously thought.

"The results shatter the notion that sophisticated forms of cognition can only be found in our 'smart' human species," said Joel Fagot, director of research at the University of Aix-Marseille in France.

The study involved two hooded crows that were at least two years old. First, the birds were trained and tested to identify items by colour, shape and number of single samples.

Once the crows has been trained on identity matching-to-sample, the birds were assessed with relational matching pairs of items.

These relational matching trials were arranged in such a way that neither test pairs precisely matched the sample pair, thereby eliminating control by physical identity.

For example, the crows might have to choose two same-sized circles rather than two different-sized circles when the sample displayed two same-sized squares.

What surprised the researchers was not only that the crows could correctly perform the relational matches, but that they did so spontaneously, without explicit training.

"That is the crux of the discovery," said corresponding author of the study Ed Wasserman, a psychology professor at University of Iowa in the US.

"Honestly, if it was only by brute force that the crows showed this learning, then it would have been an impressive result. But this feat was spontaneous," Wasserman pointed out.

The study appeared in the journal Current Biology.