Why animals recognise numbers but only humans can do maths
A wide range of animals seem to have a grasp of numbers – but humans hold the trump card.
theconversation.com
And I remember reading a story about a mother cat with four kittens, who was moving the kittens in from the garden, one kitten at a time. Pick up a kitten, carry to new location, go back for a kitten, carry to new location. To help her the owners picked up the last two kittens and brought them in and added them to the first two kittens. Mother cat was distraught, running around out in the garden looking for the kitten pile out there. So they carried out the two kittens and put them back where they'd found them and let mother cat do her thing. They decided that she could definitely count to two - two piles of kittens, but couldn't count to four as she hadn't worked out there were now four kittens in the house.
