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.
Human interaction with cats
Cats can also come in several body types, ranging between two extremes:Because of their small size, domesticated house cats pose little physical danger to adult humans. However, in the USA cats inflict about 400,000 bites per year. This number represents about one in ten of all animal bites. Many cat bites will become infected, sometimes with serious consequences such as cat-scratch disease, or, more rarely, rabies. Cats may also pose a danger to pregnant women and immunosuppressed individuals, since their feces can transmit toxoplasmosis. A large percentage of cats are infected with this parasite, with infection rates ranging from around 40 to 60% in both domestic and stray cats worldwide. Research indicates a correlation between the parasite "Toxoplasma gondii", which sexually reproduces exclusively in cats, and numerous human psychiatric conditions, including OCD. The compulsive hoarding of cats, a symptom of obsessive compulsive disorder (OCD), has long been associated with "crazy cat ladies".