Saturday, April 7, 2012

Are Male Brains Different from Female Brains?

By now, everyone has heard of the Canadian parents have chosen not to reveal the gender of their child, Storm. Of course, there are people who will know, the doctor, the parents and anyone who changes a diaper, but the parents feel that by not revealing the child’s gender, they can raise a gender free child. An obvious first dilemma is what pronouns to use to talk about the child, but more important is the question of whether one can raise a gender free child. Is gender biological or cultural or a mixture?

We know that there are biological differences between males and females. There is a difference in one pair of genes. There are differences in hormone secretions between males and females. Males, on average, tend to be larger than females. The center of balance in females is lower than in males. At puberty, there are a number of changes that differentiate males from females.  Aside from these, there is a question of if there are differences between the male and female brain. The short answer is yes, there are.

It is known that the different sex hormones (estrogen, progestin, testosterone and androgen) affect the development of the brain and differences in brain development have been seen as early as 26 weeks gestation, indicating that these influences are present from very early in fetal development. On average, the male brain is slightly larger than the female brain (as a percentage of overall body size) but some structures are bigger in males and others are bigger in females, which may account for the difference in size.  An example of this is that the limbic cortex (responsible for regulating emotions) is larger in women and the parietal cortex (having to do with space perception) is larger in men.

Another difference is that men have far more (6.5 times) gray matter than women but women have even more white matter (10 times) than men.  Gray matter is neurons, white matter is full of synapses which may mean that women’s brains process faster than men’s.  There is some evidence that neurons are more tightly packed in women’s brains, which would mean that they take up less space.

Since that advent of techniques that can observe the brain at work (such as magnetic resonance imaging and tomography) scientists have discovered that men process language on one side of the brain but women activate parts on both sides of the brain when processing language. The corpus callosum (the part of the brain that connects the two sides) is larger in women too, which might make communication between the two sides faster and easier in women. (It has been suggested that this may be why learning disorders such as dyslexia are more common in males.)

The question then becomes, Are the differences in the brain responsible for the different stereotypes we have for men and for women?  The answer here is not so simple. For one thing, there are certain disabilities that are seen more in one sex over the other. Some of these, such as dyslexia (which is more common in boys) and dementia (more common in women) may be related to physical differences in the brain.

Although the research in not conclusive, there is a suggestion that different parts of the brain develop at different rates in males and females. This would mean that girls would excel at some things and boys at others at certain ages, even though they would equal out in a few more years. The problem with this is that during the learning years, equal performance is expected and at the higher level. In areas where one gender excels, members of the other could get the idea that they are not as good and might give up on those subjects (math for girls and language skills for boys.) If this is true than care needs to be taken to encourage each so that they have confidence by the time their brain is ready for the subject.

There is evidence that people react differently to girls than to boys from the first day. Studies in newborn nurseries have shown that parents use adjectives like dainty, pretty and sweet to describe girls and adjectives like strong, husky and active to describe boys in the first days of their lives, regardless of the birth weight of the child. Girls are dressed in cute little flowery things and boys in football jerseys for the trip home from the hospital. Toy choices are different from the start as can be the color and theme of the nursery. These are influences that have little to do with brain structures. These are the influences that Storm’s parents are trying to minimize. Since they obviously know the gender of the baby, will they be able to control their own well-learned biases regarding gender? What influence it will have on Storm remains to be seen.

Until recently, social roles demanded differences between the genders. Women were often pregnant and providing direct care for young children during their adult life and men were handling the support chores such as finding food and providing safe environments for the offspring. These roles led to different behaviors. Scientists debate whether the biological differences in the brain caused the different roles or whether the different roles caused the biological differences in the brain. Now, with technological advances, women can provide food and safe environments for the offspring. Men can then spend more time in the direct care of their children. Perhaps these role changes will affect brain structures of the future.

Many articles were read to write this article. A partial list follows.
Edmonds, Molly, Do men and women have different brains? Discovery Health, “Male and Female Brain Structure” published online
Kanazawa, S, Male brain vs. female brain !, Psychology Today online, created Mar 2008.
Sabbatini, R, Are there differences between the brains of Males and Females, Mind and Behavior, online 1997
Witt, S, Parental Influence on Children’s Socialization to Gender Roles, online , 1997. This one contains a long bibliography or articles on related subjects.

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