Cat intelligence
The brain of the domesticated cat is about long, and weighs . If a typical cat is taken to be long with a weight of , then the brain would be at 0.91% of its total body mass, compared to 2.33% of total body mass in the average human. Within the encephalization quotient proposed by Jerison in 1973, values above 1 are classified big brained, while values lower than 1 are small brained. The domestic cat is attributed a value of between 1–1.71 relative to human value that is 7.44–7.8. The largest brains in the Felidae family are those of the tigers in Java and Bali, of which the largest relative brain size within the "panthera" is the "tigris". It is debated whether there exists a causal relationship between brain size and intelligence in vertebrates. Correlations have been shown between these factors in a number of experiments. However, correlation does not imply causation. Most experiments involving the relevance of brain size to intelligence hinge on the assumption that complex behavior requires a complex (and therefore intelligent) brain; however, this connection has not been consistently demonstrated.
Smilodon
Another argument for sociality is based on the healed injuries in several "Smilodon" fossils, which would suggest that the animals needed others to provide it food. This argument has been questioned, as cats can recover quickly from even severe bone damage and an injured "Smilodon" could survive if it had access to water. The brain of "Smilodon" was relatively small compared to other cat species. Some researchers have argued that "Smilodon"'s brain would have been too small for it to have been a social animal. An analysis of brain size in living big cats found no correlation between brain size and sociality. Another argument against "Smilodon" being social is that being an ambush hunter in closed habitat would likely have made group-living unnecessary, as in most modern cats. Yet it has also been proposed that being the largest predator in an environment comparable to the savanna of Africa, "Smilodon" may have had a social structure similar to modern lions, which possibly live in groups primarily to defend optimal territory from other lions (lions are the only social big cats today).