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Not all animals have neurons; Trichoplax and sponges lack nerve cells altogether. Neurons may be packed to form structures such as the brain of vertebrates or the neural ganglions of insects. The number of neurons and their relative abundance in different parts of the brain is a determinant of neural function and, consequently, of behavior.
Brain of a human (left), compared to that of a black rhinoceros (center) and a common dolphin (right). Elephant brains also show a complexity similar to dolphin brains, and are also more convoluted than that of humans, [20] and with a cortex thicker than that of cetaceans. [21]
Compared to that of other mammals, the pulvinar region of the brain – which helps to visually detect relevant objects – is disproportionately large and effective in the brains of primates (including humans). The concept of snakes being a special threat to humans has been confirmed by population-based studies.
As in larger brains, two basic neural architectural principles of many invertebrate brains are the existence of specialized brain structures and circuits, which refer to specific sensory domains, and of higher-order integration centres, in which information pertaining to these different domains converges and is integrated, thus allowing cross ...
Animals that form pair bonds and share parental responsibilities produce offspring that are more likely to survive and reproduce, which increases the fitness of these individuals. The cognitive requirements for this type of mating include the ability the differentiate individuals from their group and resolve social conflicts.
Though these criteria are difficult to measure in nonhuman animals, cephalopods are the most intelligent invertebrates. The study of cephalopod intelligence also has an important comparative aspect in the broader understanding of animal cognition because it relies on a nervous system fundamentally different from that of vertebrates. [3]
Comparing brain size at birth to the size of a fully developed adult's brain is one way to estimate how much an animal relies on learning as opposed to instinct. The majority of mammals are born with a brain close to 90% of the adult weight, [ 23 ] while humans are born with 28%, [ 23 ] bottlenose dolphins with 42.5%, [ 24 ] chimpanzees with 54 ...
Similarly sized brains, such as a cow or chimpanzee, might in that scenario contain very different numbers of neurons, just as a very large cetacean brain might contain fewer neurons than a gorilla brain. Size comparison between the human brain and non-primate brains, larger or smaller, might simply be inadequate and uninformative – and our ...