Nervous system

The reptilian nervous system contains the same basic part of the amphibian brain, but the reptile cerebrum and cerebellum are slightly larger. Most typical sense organs are well developed with certain exceptions most notably the snake's lack of external ears (middle and inner ears are present). There are twelve pairs of cranial nerves.

Reptiles are not generally considered particularly intelligent when compared to mammals and birds. Their brains fall well below those of mammals in size relative to the body, the encephalisation quotient being about one tenth of that of mammals. The crocodiles have brains in the higher size range and show a fairly complex social structure. Larger lizards like the monitors are known to exhibit complex behaviour, including cooporation. The Komodo dragon is known to engage in play.