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Brain to body mass ratio (also known as the Encephalization Quotient or EQ) is a rough estimate of the possible intelligence of an organism. Image File history File links Broom_icon. ... 1. ... In mathematics, a quotient is the end result of a division problem. ... Intelligence is the mental capacity to reason, plan, solve problems, think abstractly, comprehend ideas and language, and learn. ... This article does not cite any references or sources. ...

It is defined as the ratio of the actual brain mass to the expected brain mass of a typical animal that size, EQ=m(brain)/Em(brain). The formula for the expected mass of the brain varies, but is usually Em(brain) = 0.12m(body)^{2 / 3} where masses are in grams, though for some classes of animals the power is 3/4 rather than 2/3.

Roughly speaking, the larger an organism is, the more brain mass is required for housekeeping tasks, such as breathing, thermoregulation, senses, motor skill, etc.^{[citation needed]} The larger the brain is relative to the body, the more brain mass might thus be available for more complex cognitive tasks. This method, as opposed to the method of simply measuring brain mass alone, puts humans closer to the top of the list. Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when temperature surrounding is very different. ... A motor skill is a skill that regards the ability of an organism to utilise skeletal muscles effectively. ... Look up Cognition in Wiktionary, the free dictionary. ... Human beings are defined variously in biological, spiritual, and cultural terms, or in combinations thereof. ...

Rather than simply dividing brain mass by body mass, some divide brain mass by the ⅔ power of body mass (in other words, divide brain mass by body surface area) or the ¾ power of body mass.

Dolphins have the highest brain to body mass ratio of all cetaceans. Sharks have the highest for a fish, and octopuses have the highest for an invertebrate. Humans have a higher brain to body mass ratio than any of these animals. Genera See article below. ... Suborders Mysticeti Odontoceti (see text) The order Cetacea includes whales, dolphins and porpoises. ... Orders Carcharhiniformes Heterodontiformes Hexanchiformes Lamniformes Orectolobiformes Pristiophoriformes Squaliformes Squatiniformes Symmoriida(extinct) Sharks (superorder Selachimorpha) are fish with a full cartilaginous skeleton[1] and a streamlined body. ... A giant grouper at the Georgia Aquarium Fish are aquatic vertebrates that are typically cold-blooded; covered with scales, and equipped with two sets of paired fins and several unpaired fins. ... Suborders †Pohlsepia (incertae sedis) †Proteroctopus (incertae sedis) †Palaeoctopus (incertae sedis) Cirrina Incirrina Synonyms Octopoida Leach, 1817 The octopus (Greek , eight-legs) is a cephalopod of the order Octopoda that inhabits many diverse regions of the ocean, especially coral reefs. ... Invertebrate is a term that describes any animal without a spinal column. ...

It is a trend that the larger the animal gets, the smaller the relative brain size gets. Large whales have very small brains compared to their weight, and small rodents have huge brains. One explanation could be as an animals gets larger, the size of the neural cells remain the same, and more nerve cells will cause the brain to increase in size to a lesser degree than the rest of the body. This phenomena has been called the cephalization factor; E = CS², where E and S are body and brain weights, while C is the cephalization factor. Just focusing on the relationship between the body and the brain is not enough, one also has to consider the total size of the animal.

However, there seems to be some controversy over whether humans have the highest brain to body mass ratio (followed by dolphins),^[1][2][3] or whether treeshrews are on the top of the list^[4] Treeshrews hold nearly 10% of their mass in their brain, making it one of the most encephalized animals.^[5] Families Tupaiidae Ptilocercidae The treeshrews are small mammals native to the tropical forests of Southeast Asia. ... 1. ...

Since shrews are less intelligent than humans, many^{[citation needed]} believe that intelligence correlates with the absolute brain-mass left over from when one subtracts the brain-mass for running the body. In the essay "Bligh's Bounty",^[6] 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 mass of the spinal cord from the brain^{[citation needed]}. This formula is useless for invertebrates because they do not have spinal cords, or in some cases, central nervous systems. It has been suggested that Darwinian Fundamentalism be merged into this article or section. ...

See also

• Cranial capacity
• Encephalization
• Neuroscience and intelligence

Cranial capacity is a measure of the volume of the interior of the cranium (also called the braincase or brainpan) of those animals who have both a brain and a cranium. ... 1. ... // Brain size The correlation between brain size and IQ seems to hold for comparisons between and within families (Gignac et al. ...

References

1. ^ http://www.tufts.edu/as/wright_center/cosmic_evolution/docs/text/text_cult_3.html
2. ^ http://21stcentury.chinadaily.com.cn/article.php?sid=16240
3. ^ http://www.wsu.edu:8080/~taflinge/mindwork/mawint1.html
4. ^ http://www.hindustantimes.com/news/181_935198,00300006.htm
5. ^ http://www.kk.org/thetechnium/archives/2004/11/brains_of_white.php
6. ^ web archive of monash.edu.au

External links

• http://www.tufts.edu/as/wright_center/cosmic_evolution/docs/text/text_cult_3.html
• http://www.wsu.edu:8080/~taflinge/mindwork/mawint1.html
• a graph of body mass vs. brain mass
• "Bligh's Bounty" — Stephen Jay Gould