It all starts in the playground on the swings. Little Johnny argues with the little Sally and makes the assertion that “boys are smarter than girls”. She obviously doesn’t take that lying down and comes back with “NO! Girls are smarter than boys”. So he retaliates with a statement like “girls are stupid”. In return she rightfully stands up for her gender and defends them by saying, “girls are smart and boys are stupid and silly”. Not knowing it at the time, these two little munchkins grow up with these propositions in the backs of their minds and eventually conduct research on how the brains differ between genders. Is it really the case that we can conclude one is smarter than the other?

The hormone that gives the male physical qualities is testosterone, while the one giving the female physical qualities is estrogen. The differences caused by these two hormones between men and women go beyond the external appearances and actually manifest themselves down at the subcellular level. The sizes of compartments within neurons and between different cellular groups are affected directly by the actions of estrogen and testosterone.

When they’re born, the brains of boys and girls are the same size and they stay that way until they reach the age of 2 years. At that point boys’ brains grow faster until the full adult brain size is reached at 6 years of age. By the time they’re fully grown, men’s bodies are on average only about 8% larger than women’s. But the male brain at this point is 15% larger. This doesn’t necessarily mean they’re better. While the physical size might look like it can hold more information, it might take longer for communication between different parts (total speculation and not proven scientifically but I’m sure many women would love to explain away how slow men are sometimes!).

Aside from the overall size difference, different parts show different size ratios between men and women’s brains. For example, there is a wide band of axons (neuroscience term for ‘connections wires’) called the corpus callosum that connects the two halves of the brain and allow communication between them. Studies have shown the corpus callosum to be thicker in women than in men.

A thicker corpus callosum means that women have more intercommunication between the two hemispheres. This in turn means that women tend to use both sides of their brains for functions such as speech and spatial navigation. Men on the other hand have what are called “asymmetries in function”, which means they use one side of their brain for the same functions that women can recruit both sides for. The thicker corpus callosum might be a reason why women show fewer and less severe neurological and cognitive deficits if they sustain a head injury. Also, having the female hormone progesterone appears to reduce brain swelling after injury in women.

However, functional asymmetry might be advantageous for specialized tasks. The domination of the male population in math and engineering departments can be potentially explained by the lessened intrusion of function from the right hemisphere into the left hemisphere. Hence, the left side of a male brain can focus on those equations without being distracted by thoughts of what the numbers could possibly represent in the abstract sense.

Could it be possible that the increased intercommunication between the “logical/calculating” left hemisphere and the “abstract/emotional” right hemisphere result in increased personal involvement in decision-making? It would be an interesting explanation as to why women seem to show more emotional investments in certain decision than men.

Androgens such as testosterone contribute to an increase in asymmetry of men’s brains. The cerebral cortex, which is important in memory, attention, thought, language, and consciousness, is thicker in the right hemisphere in the male brain than in the female one. It’s been previously shown that androgens suppress the growth of the left side, which is now being debated as a possible reason for the higher ratio of learning and language disabilities seen in males than females. Furthermore, the prefrontal cortex region (shown in the green-shaded area below), where executive function and decision making take place, continues to form its connections well into the mid to late twenties for men, but is fully matured in women in their early twenties. This would explain why the phrase “grow up” is almost exclusively used by women when they speak to men – before they’re 30, this phrase is unfortunately shouted out in vain.

Looking at PET scans of brain activity, some interesting findings have been observed. Women have 15% greater blood flow in the cerebral cortex and have a greater overall brain energy metabolism than men.  They also have higher activity levels in the cingulate gyrus, which is an important region having roles in emotion formation and processing, decision making, learning and memory.

PET scans of men’s brains revealed higher activity levels in the temporal lobe, cerebellum, and the limbic system. The temporal lobe handles perception of sound, derivation of meaning from speech and vision, ability for spatial navigation, and the formation of long-term memory. The cerebellum is important for coordination of movement, and has roles in attention and language, and in regulating fear and pleasure reactions. The limbic system handles emotion, behavior and long-term memory.

The higher activities in these areas explain why some gender differences are noted when men and women are behaviourally tested. For example, men and boys learn road maps and different routes faster and with fewer errors than women and girls. However, women and girls can recall more landmarks along the same routes they didn’t score that well on as opposed to men and boys. Another difference is in sports. Having a more active cerebellum explains the generally higher performance of male athletes in comparison to their female counterparts, as well as their general tendency to participate in more extreme sports.

What’s really interesting is how this information can relate to everyday life. Since women have better and more efficient intercommunication that allows for the use of both sides of their brains, it would explain their higher capacity for seeing the abstract meanings behind the outwardly concrete information, such as the case in reading fiction. In fact, women are reported to be over twice as likely as men to read fiction novels. The gender-based brain differences would serve as an explanation for why they might have a greater appreciation for such works.

On the other hand, when women claim that men never listen, that might be more a case of the man being rude than not being able to. In fact, having more activity in the temporal lobes than women indicates that men’s capacity for not only perception of sound, but also derivation of meaning from sound and body language are perfectly in tact. Men also have higher activities in the cerebellum, which is responsible for attention, and in the limbic system, which handles emotion.

So in short, a man should have a higher capacity to pay attention, listen closely, and understand what’s being said, and react emotionally when his wife is trying to talk to him about something. Men in general have higher ratios of language and learning disabilities due to their testosterone and thinner corpus callosum, both of which result in an asymmetry of function. This, however, does allow men to compartmentalize function more and be able to for example think logically and make decisions without too much interference of emotions if they need to. Men also have greater capacity to focus their attention, and listen when needed. Women on the other hand are able to simultaneously draw in different capacities from both sides of their brains, derive abstract meanings in ways most men may not be able to, suffer less neurological problems due to their progesterone and thicker corpus callosum if they sustained a head injury, and rather than focus on the route of getting between destinations, they focus on the experience of it and enjoy the landmarks they pass on the way (next time you go travelling with a group to an unfamiliar destination, take note of who remembers what they saw and who remembers how to get between different places).

The bottom line is that men and women have different capacities and neither is better overall. The complement of the two is needed to generate the whole and obtain the best outcome. It’s quite clear from a neuroscientific perspective that building a healthy society would require the equal participation of both of the active brains of men and women.