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 will is always right.”
—Jean-Jacques Rousseau (1712–1778)
“I may be able to spot arrowheads on the desert but a refrigerator is a jungle in which I am easily lost. My wife, however, will unerringly point out that the cheese or the leftover roast is hiding right in front of my eyes. Hundreds of such experiences convince me that men and women often inhabit quite different visual worlds. These are differences which cannot be attributed to variations in visual acuity. Man and women simply have learned to use their eyes in very different ways.”
—Edward T. Hall (b. 1914)
“When we say that pleasure is the end, we do not mean the pleasure of the profligate or that which depends on physical enjoyment—as some think who do not understand our teachings, disagree with them, or give them an evil interpretation—but by pleasure we mean the state wherein the body is free from pain and the mind from anxiety.”
—Epicurus (c. 341–271 B.C.)
“If they’ve a brain and cerebellum, too,
They’ve got to leave that brain outside,
And vote just as their leaders tell ‘em to.”
—Sir William Schwenck Gilbert (1836–1911)
“Men have defined the parameters of every subject. All feminist arguments, however radical in intent or consequence, are with or against assertions or premises implicit in the male system, which is made credible or authentic by the power of men to name.”
—Andrea Dworkin (b. 1946)