Encephalization Quotient - Comparisons With Non-mammalian Animals

Comparisons With Non-mammalian Animals

Dolphins (which are mammals) have the highest brain-to-body weight ratio of all cetaceans. Manta rays have the highest for a fish, and either octopuses or jumping spiders have the highest for an invertebrate. Despite the jumping spider having a huge brain for its size, it is minuscule in absolute terms, and humans have a much higher EQ, despite having a lower raw brain-to-body weight ratio. Mean EQ for reptiles are about one tenth of the EQ for mammals. EQ in birds (and estimated EQ in dinosaurs) generally also falls below that of mammals, possibly due to lower thermoregulation and/or motor control demands. Estimation of brain size in the oldest known bird, Archaeopteryx, shows it had an EQ well above the reptilian range, and just below that of living birds.

In the essay "Bligh's Bounty", Stephen Jay Gould noted that if one looks at vertebrates with very low encephalization quotients, their brains are slightly less massive than their spinal cords. Theoretically, intelligence might correlate with the absolute amount of brain an animal has after subtracting the weight of the spinal cord from the brain. This formula is useless for invertebrates because they do not have spinal cords, or in some cases, central nervous systems.

Read more about this topic:  Encephalization Quotient

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