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The size of the brain is a frequent topic of study within the fields of anatomy, biological anthropology, animal science and evolution.Measuring brain size and cranial capacity is relevant both to humans and other animals, and can be done by weight or volume via MRI scans, by skull volume, or by neuroimaging intelligence testing.
One early suggestion was brain size (or weight, which provides the same ordering.) A second proposal was brain-to-body-mass ratio, and a third was encephalization quotient, sometimes referred to as EQ. The current best predictor is number of neurons in the forebrain, based on Herculano-Houzel's improved neuron counts. [1]
Brain size usually increases with body size in animals (i.e. large animals usually have larger brains than smaller animals); [4] the relationship is not, however, linear. Small mammals such as mice may have a brain/body ratio similar to humans, while elephants have a comparatively lower brain/body ratio. [4] [5]
The relationship between brain size, body size and other variables has been studied across a wide range of vertebrate species. As a rule of thumb, brain size increases with body size, but not in a simple linear proportion. In general, smaller animals tend to have proportionally larger brains, measured as a fraction of body size.
After all of the data, all observations concluded that the main development that occurred during evolution was the increase of brain size. [52] However, recent research has called into question the hypothesis of a threefold increase in brain size when comparing Homo sapiens with Australopithecus and chimpanzees. For example, in an article ...
The human brain and the cat brain both have cerebral cortices [13] with similar lobes. [14] [failed verification] The number of cortical neurons contained in the brain of the cat is reported to be 203 million. [15] Area 17 [16] of the visual cortex was found to contain about 51,400 neurons per mm 3. [17] [18] Area 17 is the primary visual ...
Encephalization quotient (EQ), encephalization level (EL), or just encephalization is a relative brain size measure that is defined as the ratio between observed and predicted brain mass for an animal of a given size, based on nonlinear regression on a range of reference species.
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. Brain of the sperm whale, considered the largest brain in the animal kingdom. Sperm whales (Physeter macrocephalus) have the largest known brain mass of any ...