User:Kiianamariiee/Brain size

In humans, the right cerebral hemisphere is typically larger than the left, whereas the cerebellar hemispheres are typically closer in size. The adult human brain weighs on average about 1.5 kg (3.3 lb). In men the average weight is about 1370 g and in women about 1200 g. The volume is around 1260  cm3 in men and 1130  cm3 in women, although there is substantial individual variation. Yet another study argued that adult human brain weight is 1,300-1,400g for adult humans and 350-400g for newborn humans. There is a range of volume and weights, and not just one number that one can definitively rely on, as with body mass. It is also important to note that variation between individuals is not as important as variation within species, as overall the differences are much smaller. The mechanisms of interspecific and intra specific variation also differ. Brain size has also been linked to body size, through various autopsy's performed there is a correlation between brain mass, stature, and body mass of about 0.20. Autopsy's have shown the quickest growth in brain mass is within the first year of life, the brain continues to grow at a peak in teenage years and continues to slowly grow. Eventually, as one gets older, brain mass begins to decrease. There is a difference in weight at about 397g at birth, and increases to about 1,180 g by the age of 6.

Not all investigators are happy with the amount of attention that has been paid to brain size. Roth and Dicke, for example, have argued that factors other than size are more highly correlated with intelligence, such as the number of cortical neurons and the speed of their connections. Moreover, they point out that intelligence depends not just on the amount of brain tissue, but on the details of how it is structured. It is also well known that crows, ravens, and grey parrots are quite intelligent even though they have small brains. It has been suggested that patterns of human brain evolution were influenced by collective intelligence. In an investigation by Pakkenberg and Gundersen, they had found that men had about 4 billion more cortical neurons than did women, but was not accounted for by height. It was found that although women have proportionately smaller brains than do male, they share the same intelligence test scores.