A recent magnetic resonance imaging study has shown that it is possible to distinguish males and females with an accuracy of 93 per cent just using brain images.
Julio Duarte-Carvajalino and colleagues from UCLA used diffusion tensor imaging in a study reported in the journal Neuroimage. Diffusion tensor imaging is a new process by which connections between different parts of the brain (made by the white matter fibres, which are like tiny wires) can be imaged.
They found that female brain connections were more symmetrical and had more connections from the left side of the brain to the right; male brains tended to be asymmetrical and had more connections between areas on one side of the brain.
The researchers found no interactions with age between the ages of seven and 22 (the ages of the persons studied), showing that these changes are not due to different cultural experiences.
Men are known to be better at visual orientation than women, and this gender difference has been found in infants as young as three months.
Men are better at rotating an object in their mind. Women have better verbal fluency and a better memory for objects. They remember better where things have been put. Men are better at navigating by cardinal direction (for example going northwards), whereas women tend to navigate using landmarks.
Personality differences between the sexes have been thought to be small but Marco Del Giudice, from the University of Turin, reporting in the journal PLOS One, found extremely large differences between men and women in a large US sample of over 10,000 people.
It was noted that personality differences between the sexes have been consistently underestimated in the past because of inadequate methodology.
One commonly quoted theory is that men and women start off with a single type of ‘intersex’ brain and that individuals’ personalities are made up of a mosaic of ‘masculinizing’ or ‘feminizing’ influences.
In April, Larry Cahill, professor of neurobiology and behaviour at the University of California, Irvine, wrote in Cerebrum that there is no evidence to support this. There is a limit to how much the brain can be changed by training, as, for example, a left-handed person who is forced to use the right hand will never be as good with the trained right hand.
The definition of ‘gender identity’ in the proposed law appears to be superficial and seriously lacking
People’s brains are not just a ‘blank slate’ that is mouldable, and we are just beginning to discover how large are the inherent differences in structure and function between the sexes.
New interesting research is also beginning to emerge on differences in moral judgments between the sexes.
Manuela Fumagalli and colleagues from the University of Milan studied how men and women responded to several personal moral dilemmas.
For example, they were told to imagine they were a doctor and they had five dying patients who could only be saved by transplanting five organs from a young man against his will and that this would kill him. They had to give a quick yes or no answer.
The researchers found that men were more likely to make ‘utilitarian’ judgements than women and would be more likely to choose to transplant in this situation.
In a separate study, Dan Bouhnik, from Israel, found girls were more likely to make a ‘humane’ judgement and tended more towards judgements that reflected adherence to peer-group conventions than boys.
These findings have implications for the new proposed legislation on gender in Malta. What is being proposed is that individuals who feel they have the wrong gender can freely and easily choose to change their gender.
‘Gender identity’ is defined in the proposed law as “each person’s internal and individual experience of gender, which may or may not correspond with the sex assigned at birth”.
Research is telling us we have a hard-wired brain structure that underlies the sex-specific way we act. We can change the external way we act and look into that of the opposite sex but it is likely that a lot of the actions and decisions of transsexual people will be strongly influenced by the brain structure of their original sex.
The definition of ‘gender identity’ in the proposed law appears to be superficial and seriously lacking. Something that is so deeply written in our brain should not be changeable by a simple application to the Director of the Public Registry.
An unhurried period of consultation with experts and assessments to ensure the right decision is being made and that the individual knows all the risks and implications should be mandatory.
Patrick Pullicino is a neurologist.