Once they see the animal, they dive and pin it to the ground, letting a human or gun-dog retrieve the carcass.

WSJ: Learn Ancient Sports Around the World

That has led to concerns that the birds used to make the eggs themselves could succumb to bird flu. (The companies emphasize that the chickens are kept under extremely secure conditions.) There is research going on to use dog, monkey or human cell cultures to produce flu shots, but such production is five to ten years away.

FORBES: Flu Shot Gold Rush

Researchers concluded that any such "guilty look" is a response to human behaviour and has no relation with the dog's actions or sense of having broken any rules.

BBC: Can dogs really look 'guilty'?

Whereas every dog lab now tests the cognition of its animals while their human owners are blindfolded or asked to face away, young children are still presented with cognitive tasks while sitting on their mothers' laps.

WSJ: The Brains of the Animal Kingdom