Toy story - Are the sexes really alien to one another? Science knows the true differences between men and women...

Why do girls prefer dolls and boys cars? Some put in down to cultural influences that prepare children to take on stereotypical gender roles adults. Now consider this: male vervet monkeys prefer cars even though they have never been primed to do so (Evolution and Human Behavior, vol 23, p 467), and girls who have a hormonal disorder that means they produce too much testosterone prefer them, too. This suggests an innate component to toy choice, which may be amplified by socialization processes after birth.

Intriguing new research by Margareth McCarthy at the University of Maryland in College Park points to the neurobiology underlying sex-specific play preferences – in rats, at least. Her group found that the amygdalae, twin brain structures that are important for processing emotional and social cues, contain between 30 and 50 per cent more of a type of brain cell called glial cells in female rats than in males. Male brains, meanwhile, had higher levels of endocannabinoids – naturally occurring molecules that stimulate the same neural circuits as the active ingredient in cannabis.

However, when the researchers injected day-old-female rats with a dose of a cannabis-like substance, they found that after three days the proportion of glial cells in their amygdalae was the same level as in males. These females now played like male pups too-they played 30 to 40 per cent more than regular females, and indulged in much more rough-and-tumble play (Proccedings of the National Academy of Sciences, vol 107, p 20535).

The main structural differences between male and female rat brains all have parallels in humans, and researchers believe that all mammals have the same neural mechanisms underlying key survival behaviours. Yet whether such similar neurobiology underpins play differences among children is unknown.

What is clear is that human behaviour is highly adaptaple, and this includes play and other behaviours that differ between the sexes. What goes on before birth and shortly afterwards is not the ultimate determinant, says McCarthy. “In the human brain, we think there´s a lot that experience can do.”

Source: Venus and Mars collide. (New Scientist, March 5th, 2011)

Glossary:

Vervet: (noun) South African monkey with black face and hands;

 Primed: (verb): to prime. To prepare someone to behave or react in a particular way;

 Cues: (noun):  a stimulus that provides information about what to do;

 Glial: (adjective):  of or relating to neuroglia;

 Cannabis: (noun):  the most commonly used illicit drug; considered a soft drug, it consists of the dried leaves of the hemp plant; smoked or chewed for euphoric effect;  any plant of the genus Cannabis.

Day-old female: one day old; 

Pups: (noun):  young of any of various canines such as a dog or wolf; an inexperienced young person; verb:  birth; 

Indulged: (verb):  give free rein to ("The writer indulged in metaphorical language"); verb:  enjoy to excess; verb:  yield (to); give satisfaction to; verb:  treat with excessive indulgence; 

Rough-and-tumble: (noun):  disorderly fighting; adjective:  characterized by disorderly action and disregard for rules ("A rough-and-tumble fight"); 

Underpins: (verb):  support from beneath; support with evidence or authority or make more certain or confirm.