It seems Rooks appear to have a better understanding of how gravity works than chimps and babies under 6 months old.
Apparently a common way of finding out whether animals and babies understand complex concepts is to show them images of impossible events. The idea is that viewers spend longer looking at those which defy their expectations, it is assumed they are trying to work out what's going on.
Chris Bird (Cambridge Univerity) and Nathan Emery (University of London), showed rooks computer-generated images, half of which were impossible according to the laws of gravity, such as an egg floating in mid-air above a table. Almost without exception, the rooks spent more time looking at the "impossible" images than the possible ones. They also took more second glances.
The responses were the same when the "familiar" egg shape was replaced by a cork, proving the birds' insight applied equally to any object, familiar or not. The researchers say the result is consistent with rooks being able to solve complex problems from knowledge of cause and effect, rather than by trial and error.
Alex Kacelnik, who studies corvid intelligence at Oxford was surprised that chimpanzees "failed" the same test.
It could be that chimps may respect gravity but fail to infer its presence in a virtual scene between external objects, but I also find this a striking inability