![]() ![]() In 2014, it was shown for the first time that a species of dolphin, the long-finned pilot whale, has more neocortical neurons than any mammal studied to date including humans. For example, the echidna has a highly developed brain, yet is not widely considered very intelligent, though preliminary investigations into their intelligence suggest that echidnas are capable of more advanced cognitive tasks than were previously assumed. While a complex neocortex usually indicates high intelligence, there are exceptions. It is generally agreed that the growth of the neocortex, both absolutely and relative to the rest of the brain, during human evolution, has been responsible for the evolution of human intelligence, however defined. Structure Brain of a common dolphin (right), compared to that of a black rhinoceros (center) and a human (left)Įlephant brains also show a complexity similar to dolphin brains, and are also more convoluted than that of humans, and with a cortex thicker than that of cetaceans. Such a discovery may suggest a convergent evolution of these species. : 242 Spindle neurons appear to play a central role in the development of intelligent behavior. Humans, great apes, and elephants, species all well known for their high intelligence, are the only others known to have spindle cells. Spindle cells (neurons without extensive branching) have been discovered in the brains of the humpback whale, fin whale, sperm whale, orca, bottlenose dolphins, Risso's dolphins, and beluga whales. Humans are born with 28% of the adult brain weight, chimpanzees with 54%, bottlenose dolphins with 42.5%, and elephants with 35%. The majority of mammals are born with a brain close to 90% of the adult brain weight.The La Plata dolphin has an EQ of approximately 1.67 the Ganges river dolphin of 1.55 the orca of 2.57 the bottlenose dolphin of 4.14 and the tucuxi dolphin of 4.56 In comparison to other animals, elephants have an EQ ranging from 1.13 to 2.36 : 151 chimpanzees of approximately 2.49 dogs of 1.17 cats of 1.00 and mice of 0.50. The encephalization quotient varies widely between species.However, this comparison is complicated by the large amount of insulating blubber Delphinoidea brains have (15-20% of mass). ![]() In some dolphins, it is less than half that of humans: 0.9% versus 2.1%. The brain to body mass ratio (not the encephalization quotient) in some members of the odontocete superfamily Delphinoidea (dolphins, porpoises, belugas, and narwhals) is greater than modern humans, and greater than all other mammals (there is debate whether that of the treeshrew might be second in place of humans).This is slightly greater than that of humans (1,300–1,400 grams) and about four times that of chimpanzees (400 grams). Bottlenose dolphins ( Tursiops truncatus) have an absolute brain mass of 1,500–1,700 grams.Orcas ( Orcinus orca) have the second largest known brain mass of any extant animal.Sperm whales ( Physeter macrocephalus) have the largest known brain mass of any extant animal, averaging 7.8 kg in mature males.Comparison of actual brain size with the size expected from allometry provides an encephalization quotient (EQ) that can be used as a more accurate indicator of an animal's intelligence.īrain of the sperm whale, considered the largest brain in the animal kingdom Allometric analysis indicates that in general, mammalian brain size scales at approximately the 2⁄ 3 or 3⁄ 4 exponent of body mass. Since most of the brain is used for maintaining bodily functions, greater ratios of brain to body mass may increase the amount of brain mass available for more complex cognitive tasks. However, many other factors also affect intelligence, and recent discoveries concerning bird intelligence have called into question the influence of brain size. It is considered one of the most intelligent cetaceansĬetacean intelligence is the overall intelligence and derived cognitive ability of aquatic mammals belonging in the infraorder Cetacea (cetaceans), including baleen whales, porpoises, and dolphins.īrain size was previously considered a major indicator of the intelligence of an animal. Intellectual capacity of cetaceans A female bottlenose dolphin performing with its trainer. ![]()
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