Post No.: 0513
The right and left hemispheres of the brain are linked with different specialisations (although the brain can adapt to a degree if one part is damaged, especially if this damage is sustained when young when neuroplasticity is generally higher). For example, the right hemisphere plays a larger role in navigating through space, processing the big picture and for the emotions involved in helping us to escape from threats; and the left hemisphere plays a dominant role in language, handling fine-tuned details and for the emotions involved when pursuing opportunities.
But some claim that people are either more predominantly ‘right-brained’ or more predominantly ‘left-brained’ – ‘right-brained’ people are said to be more intuitive, visual and creative, while ‘left-brained’ people are said to be more logical, analytical and language-oriented. But this ‘right-brain/left-brain’ framework when looking at brain functions in this way is far too oversimplistic and therefore misleading. People are not simply ‘right-brained’ or ‘left-brained’, even if they might be left-handed or right-handed respectively. (~90% of humans favour their right hand but many people are right-sided in some ways and left-sided in other ways e.g. they favour their right eye but left ear, or write with their right hand but prefer to pull drinks can ring pulls with their left hand.)
There’s no simple one-to-one relationship between skull or brain structure and mental function i.e. phrenology is over-extrapolated pseudoscience. It’s not the case that there’s zero relation between the physical structures of the brain and behaviour (see brain damage victims) but phrenology takes this principle way too far. (It certainly doesn’t justify eugenics.) Some brain structures have multiple functions (pluripotentiality), some functions utilise multiple structures (degeneracy), and some structures are duplicated for (apparent) redundancy (redundancy).
We also don’t just use 10% of our brains – we use all of our brain most of the time. And we know this when even a small knock to the head can make us become at least temporarily impaired, and losing just a small physical chunk of it through brain damage can have a major effect on us.
The relative brain-to-body size ratio is not a reliable measure of a creature’s level of intelligence either. The brains of birds, like in the corvidae family, possess a far greater neuronal density than the brains of mammals, for instance. (It’s analogous to modern transistors in CPUs, which are smaller so can pack more densely compared to older, even overall physically larger, CPUs. Smaller transistors are easier to keep cool so run more energy efficiently too.) We are increasingly finding that many other animals are smarter than we originally thought – it was us who weren’t smart enough to recognise how smart they were!
The domestication of mammals like dogs and sheep has generally led to smaller brains in comparison to their wild counterparts – mainly in the limbic system, which is an area related to threat detection. This is probably because fear is at the root of all aggression and so a less fearful animal is also tamer, and tameness is selected for when domesticating an animal. This doesn’t make domestic animals necessarily stoopider… stewpidder… less smart than wild animals though – woof woof!
Adult male humans do have larger brains than adult female humans on average but, as alluded to above, a physically larger brain in absolute terms is not necessarily smarter than a physically smaller brain – brain size is generally correlated with level of intelligence but there are many exceptions to this relationship. And although the brains of human men and women on average appear structurally different (e.g. men tend to have larger amygdalae, women tend to have larger hippocampi, and the grey-to-white matter ratios in certain areas appear different) there are no fundamental differences between the sexes; and even those structural differences are disputed because they might be more to do with differences that simply arise because of the overall differences in average brain sizes.
There’s greater variance between different individuals than between different sexes – an analogy is that the Irish may drink more stout per head on average than the English, but we must still treat every Irish and English person on an individual basis because some English people drink more and some Irish people drink less. Summary statistics like averages only apply to the sample or population as a whole and not necessarily to any individual within that sample or population, never mind necessarily anyone inferred from a selected sample.
It’s not to say that there is no functional ‘sexual dimorphism’, or cognitive differences between the sexes, whatsoever – neurochemical differences are present due to the brains of different sexes experiencing different levels of hormones such as androgens and oestrogens, even before people hit puberty (e.g. boys tend to be better at targeting and spatial tasks like mental rotation, while girls tend to be better at verbal and certain memory tasks). One gender isn’t overall better or worse than any other – just different, again on average.
The index finger-to-ring finger (2D:4D) ratio has been found to correlate with the level of testosterone that one was exposed to when in the womb. A lower ratio (a relatively long ring finger compared to index finger) appears to indicate a higher prenatal androgen exposure. Male humans tend to have lower ratios compared to female humans. Although there’s far more to behaviour and ability than what’s mediated by testosterone – mental spatial manipulation, assertiveness, risk-taking and competitiveness are more associated with ‘masculine brains’, and language, communication, empathy and compassion are more associated with ‘feminine brains’. But once again, there’s so much variance within each sex, and overlap between the sexes, that one must treat every person as an individual rather than according to their stereotype.
Cultural gender stereotypes might also aggravate, or might arguably even totally explain, many of these differences (e.g. a culture that expects boys to be good at spatial tasks and expects girls to be good at verbal tasks). Yet there’s still currently no solid consensus as to why autism is more prevalent in males and why depression is more prevalent in females, for instance? Possible theories or hypotheses for these include that autism is an expression of an ‘extreme male brain’, and women face more hormonal fluctuations during their lives due to the menstrual cycle.
So as to whether it’s nature or nurture that explains any sex differences – it’s most probably both nature and nurture. Biological hormones play a role, as well as how people are raised, such as consciously buying more ‘boys toys’ for boys and more ‘girls toys’ for girls, or subconsciously protecting a girl more carefully than a boy and expecting a boy to take more risks than a girl. Children are also exposed to the cultural messages conveyed about gender and other (e.g. about skin colour or physical abnormality) stereotypes in fairy tales and other stories aimed at young children.
However, based on studies with monkeys and chimps (who haven’t been exposed to human toys or cultural gender stereotypes), it can be possibly inferred that young females do naturally prefer to play with dolls and play caring roles, and young males do naturally prefer to play with trucks and play rough, and it’s less to do with culture and upbringing than we may think. It may be politically correct to think that boys and girls are only nurtured into playing with certain toys, but toy preference does likely have some natural basis – with girls generally preferring to play with dolls and boys generally preferring to play with mechanical objects. Boys and girls generally play differently too, with boys tending to play rougher and girls showing more care. Play is learning in a safe environment, and in this case it’s related to learning about the likely future roles one will perform in adulthood, and these roles undoubtedly have some genetic influence for only women have wombs and men tend to grow physically stronger. Blame nature and evolution if you don’t like this setup!
Sex isn’t just a social construct or just based purely on our own individual choices. (Nowadays, ‘sex’ is regarded as biologically definable, whereas ‘gender’ is regarded as one’s selected social gender identity. The words are often used interchangeably in ordinary usage though.) Yet there is a general reluctance to study differences between the sexes (as in conducting experiments where we separate the findings according to sex) for assuming that there are no differences and that everyone is equal in every single way (the sexes are equal overall but not in the same ways – similar to how the fighter, mage, thief, cleric and ranger character classes in fantasy games are when they start out).
But COVID-19 revealed general population differences in the severity of symptoms experienced by men and women, whether due to biological and/or lifestyle reasons, for instance. So there are calls to separate treatment research on men and women because treating them equally and without segregating sex data could be doing all sexes a disservice for we may find that some diseases affect one sex worse than another, or some drugs work better or have more side-effects for one sex than another. There is an autistic person stereotype, and it is one of a boy, hence many girls miss a diagnosis of autism due to such biases in diagnostic expectations. However, how far should we go? Should we also always separate data according to ethnicity, age and/or weight too? After all, many diseases affect some ethnicities more than others, such as sickle cell disease. It adds costs to research too.
Yet – regarding the brain – we mustn’t forget that one thing about human brains in particular is that they evolved to become quite malleable, neuroplastic and adaptable, thus human brains do get moulded and shaped greatly by environmental factors. What is (or was for ancestral human life) doesn’t mean it ‘ought’ to be that way in today’s world. So if more boys learn to be more compassionate and more girls learn that engineering is for them too then we can compensate for and meaningfully close these differences.
It’s also the case that toy marketers, parents and other adults who design, sell, gift or hand toys for or to children have tended to play to or exaggerate these natural proclivities, and therefore they could potentially use nurture to instead extenuate or mitigate these proclivities so that more girls play with mechanical toys and more boys play with dolls/figurines.
Woof. The neuroscience of sex differences is an area of science where many conclusions and theories are currently being heavily contested and strong consensuses are relatively hard to come by compared to in most other fields. Some scientists are accused of perpetuating gender stereotypes and other scientists are accused of trying to be too politically correct. Science shouldn’t be political but interpretations of data inevitably do become so in such areas. I don’t personally claim to have firm answers so please share what you think via the Twitter comment button below?