The power of brain with no doubt has been the main factor of evolution in Felidae family. The reason why about seven million years ago one brunch of this family - Paleofelids, i.e., relic cats, have died out, is very probably to be the increase of brain size and complexity of contemporary cats, Neofelids that have superseded them. This one can judge by skulls of present-day cats kept in museums as well as fossilized remains of animals, extinct and existing. At the same time it is often hard to determine the reason of changes that took place. One example is a saber-toothed tiger: one group of these tigers that became extinct only several millions years ago had unusually contemporary cat brain, though with some peculiar features. It's not clear if one should impute these peculiarities to changes in brain functioning or alterations in skull structure that had to bear a heavy mass of teeth and muscles. Apparently cat brain hasn't been exposed to considerable changes in last ten millions of years yet. In other words, the brain of a lion doesn't differ much from the brain of a domestic cat.
It is clear that the brain of lion is many times bigger than a cat brain. But is a lion cleverer than a cat? It's not necessarily at all, because a big body is packaged in a big piece of skin with many tactile receptors, and a great amount of muscles requires proper amount of nerves to control them. One may calculate the weight of brain, necessary to perform the main functions and estimate then the part of brain falls on a harder work - information processing.
The degree each kind of animal differs from the calculated standard is called "intelligence quotient", IQ. A high IQ is not necessarily reflects the level of intellect solely, it may be connected with certain requirements of living. For example, flying animals or those, swimming under water, evidently need big brain than those, just living on the ground. First, because the fulfill more complicated movements, and second, because they have to percept the environment at different visual angles, both from above and from below.
Porcupines have the smallest IQ because they are socially low active and just curl themselves up into a ball in danger. Monkeys have a high IQ not only because of high ability to learning but on account of complexity of their social life.
All representatives of Felidae family but lynx (there's no idea why) have equally high IQ. All carnivorous animals have IQ about the middle; it's much larger in some representatives of canines. Partly this is explained by the bigger size of olfactory bulbs in canines in comparison with cats; this part of brain, as its' name testifies, is responsible for processing of odor information. Indeed, a big olfactory bulb could not be housed in a short and flat skull of cat.
However the difference of sensor abilities could not utterly explain differences in brain size. A complicated social behavior of canines, wolfs, for instance is supposed to require an extra power of brain.
The main part of cat brain controls for a gymnastic, if not ballet skills. In cats cerebellum that coordinates balance and movements, is much bigger than in other mammals, major part of cerebral cortex is occupied with control of movements. The considerable part of cortex is engaged in processing of great amount of information supplied by sensitive cat ears.
Translated by Tatiana Karpova (Moscow)
(MSU, Biology faculture, Dep. zoology and ecology).