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.
Neanderthal
Neanderthals are known for their large cranial capacity, which at is larger on average than that of modern humans. One study has found that drainage of the dural venous sinuses (low pressure blood vessels that run between the meninges and skull leading down through the skull) in the occipital lobe region of Neanderthal brains appears more asymmetric than other hominid brains. In 2008, a group of scientists produced a study using three-dimensional computer-assisted reconstructions of Neanderthal infants based on fossils found in Russia and Syria. It indicated that Neanderthal and modern human brains were the same size at birth, but that by adulthood, the Neanderthal brain was larger than the modern human brain. They had almost the same degree of encephalisation (i.e. brain-to-body-size ratio) as modern humans.