General Differences in Physical Brain Parameters
See also: Sex differences in humans#Brain and nervous system and Neuroscience and intelligenceStudies have found many similarities but also differences in brain structure, neurotransmitters, and function. However, some argue that innate differences in the neurobiology of men and women have not been conclusively identified. The relationship between sex differences in the brain and human behavior is a subject of controversy in psychology and society at large.
A 2004 review in Nature Reviews Neuroscience stated that the brain's sexual dimorphism is probably determined by genes on the sex chromosomes. They likely do so by genes in cells in the gonads causing the gonads to produce sex hormones that travel to the brain which affect brain cells and also by genes in brain cells directly affecting these brain cells. In the human brain, a difference between sexes has been observed in regarding the PCDH11X/Y gene pair which is unique to Homo sapiens.
In adults, men's brains are an average of 11–12% heavier than women's brains. However, men's bodies are also larger and heavier than women's bodies. In the United States, for example, adult men are an average of 18% heavier than adult women. Some researchers propose that the brain-to-body mass ratio does not differ between the sexes. However, some argue that the brain-to-body mass ratio tends to decrease as body size increases, and a sex difference in brain size still exists between men and women of the same size. A 1992 study of 6,325 Army personnel found that men's brains had an average volume of 1442 cm3, while the women averaged 1332 cm3. These differences were shown to be smaller but to persist even when adjusted for body size measured as body height or body surface, such that women averaged 100g less brain mass than men of equal size.
Though statistically there are sex differences in white matter and gray matter percentage, this ratio is directly related to brain size, and some argue these sex differences in gray and white matter percentage are caused by the average size difference between men and women. Others argue that these differences remain after controlling for brain volume.
Read more about this topic: Sex And Psychology
Famous quotes containing the words general, differences, physical, brain and/or parameters:
“The general review of the past tends to satisfy me with my political life. No man, I suppose, ever came up to his ideal. The first half [of] my political life was first to resist the increase of slavery and secondly to destroy it.... The second half of my political life has been to rebuild, and to get rid of the despotic and corrupting tendencies and the animosities of the war, and other legacies of slavery.”
—Rutherford Birchard Hayes (1822–1893)
“The extent to which a parent is able to see a child’s world through that child’s eyes depends very much on the parent’s ability to appreciate the differences between herself and her child and to respect those differences. Your own children need you to accept them for who they are, not who you would like them to be.”
—Lawrence Balter (20th century)
“With every physical pain, my moral fiber unravels a little.”
—Mason Cooley (b. 1927)
“Why does man freeze to death trying to reach the North Pole? Why does man drive himself to suffer the steam and heat of the Amazon? Why does he stagger his mind with the mathematics of the sky? Once the question mark has arisen in the human brain the answer must be found, if it takes a hundred years. A thousand years.”
—Walter Reisch (1903–1963)
“What our children have to fear is not the cars on the highways of tomorrow but our own pleasure in calculating the most elegant parameters of their deaths.”
—J.G. (James Graham)