Even the prime minister divides household chores into ‘girl jobs' and ‘boy jobs'.
The idea that men and women are deeply, fundamentally different has informed gender roles for centuries.
However, there is no such thing as a female or male brain - according to the first search for sex differences across the entire human brain.
“You couldn’t look at a brain scan and say, ‘Oh that’s of a boy, or that’s of a girl,’” says Gina Rippon, professor of Cognitive Neuroimaging at Aston University.
“Structurally, there appear to be very few differences, which is quite a surprise to people, who have assumed for hundreds and hundreds of years that males and females are different because their brains are different. The brain is very plastic – it’s mouldable. We know that different experiences will change the brain.”
In essence, Professor Rippon believes that our 'male' and 'female' behaviour is not innate but learned as we develop. In other words, our 'plastic' brains are moulded by childhood, culture, and society's expectations.
In the new BBC Two documentary No More Boys and Girls: Can Our Kids Go Gender Free?, Dr Javid Abdelmoneim explores whether the way we treat girls and boys at a young age is at the root of persistent inequalities between men and women (the gender pay gap still stands at 18%, and female CEOs make up only 7% of the FTSE 100 companies).
Dr Abdelmoneim conducted an experiment in which he attempted to completely remove all gender differences among 23 seven year-olds from a primary school in the Isle of Wight, for six weeks of ‘gender neutral’ treatment.
Using a range of psychological measures - from self-confidence to spatial awareness - he tested the kids before and after to see if going ‘gender free’ made a difference to their achievement levels.
At the beginning of the experiment, the class were asked a number of questions around gender, including what words they would use to describe each.
“Men are better, because they are stronger, and they’ve got more jobs,” says one boy.
Another says: “I think boys are cleverer than girls, because they get into president more easily, don’t they?”
One of the girls, when asked what words best describe girls, said “pretty, lipstick, dresses, love hearts”.
The first round of tests showed the girls were seriously underestimating how clever they were, with far lower self-esteem and less confidence.
The boys, on the other hand, were more likely to overestimate their ability. They also didn’t use anywhere near the same range of vocabulary to describe their emotions.
When tested on practical skills like spatial awareness, the boys were better. Dr Abdelmoneim points out that boys often develop those skills because they’re encouraged to play with Lego or building blocks, and that makes them better equipped to deal with problems from maths to map reading.
That might be a factor in explaining why only 21% of people working in science, technology and engineering are women.
With toy brands presenting certain things as girls’ toys and others as boys’ toys, it can be hard for parents not to buy their daughters dolls and sewing kits, while their boys get trucks and lego – contributing to the different ways their brains ultimately develop.
In one experiment away from the classroom, Dr Abdelmoneim observed a group of adults who were playing with babies that had their clothes swapped with the opposite gender.
The four adults automatically chose soft toys and dolls for the ‘girl’ babies, and robots and cars for the ones they thought were boys.
It's one of countless ways that adults unwittingly impose gender stereotypes on children. And it’s exactly those kinds of attitudes that Dr Abdelmoneim hopes to change through his ‘gender free’ classroom experiment.
For six weeks, the children used the same toilets, played the same sports, and read the same books. Their teacher was careful to speak to them in the same way - not saying ‘mate’ to the boys and ‘love’ to the girls.
To challenge the kids' gender stereotypes around professions, he brought in a female magician, female mechanic, male make-up artist, and male ballet dancer for them to meet.
At home, the parents were asked to remove gendered toys, reconsider nicknames, and reassess the way chores are shared.
The children reacted positively to the experiment, apart from having to share a toilet. One girl complained: "The boys come out with their bits dangling out and they don’t wash their hands.”
After six weeks, the kids were tested again to see how these changes had influenced them – using the unchanged class next door as a control.
The results were significant. The difference in self-esteem between girls and boys dropped from 8% to 0.2%.
As one girl said: “I think I can do anything now, because I know I can be anything I want to be.”
No girls used words like "ugly" to describe themselves this time, instead opting for words like “unique” and “happy”. Their self-motivation went up by 12%, and they were 40% more accurate when predicting their scores before a test.
For the boys, their measurement of kindness towards others went up by 10%, while their ability to identify their emotions improved.
“I think the boys have learnt to be more caring," one girl said.
The biggest change observed in the boys was the reduction of bad behaviour by 57%.
“I think it’s better to express yourself rather than just getting angry,” said one, while another said: “I don’t think I strop any more because I just talk about it. I’ve learnt it’s better to talk than strop.”
After two weeks of practising with the shapes that test spatial awareness, the top 10 students in the class were split evenly between girls and boys.
“These effects are really encouraging, and show the children have started to change in ways that might have a profound effect on later life,” Dr Abdelmoneim said.
Critics have accused the experiment of putting too much emphasis on gender for impressionable young children.
Conservative party councillor Mary Douglas labelled it “abusive” and “inappropriate,” but Sophie Cook, a former Labour Party parliamentary candidate, dismissed the outcry as “unnecessary hysteria”.
Reacting to criticism, Dr Abdelmoneim responded: “This is about giving children a full development so they can achieve absolutely anything they want. I’d challenge any sane and sensible adult to say we don’t want that.”
The experiment is over but, for the class’s teacher, Mr Andre, the changes are there to stay.
“You can see a confidence in all the children that they didn’t have before – now they are challenging things, which is brilliant," he said.
“There’s a little girl in our class who couldn’t stand football, but now she’s joined a team. And you’ve got a boy going to his mum’s belly-dancing classes.
“I’ve carried on with the gender-neutral messages. I’ve shared them with the whole school. So we’re looking at not just having a gender-neutral classroom – but a gender-neutral school.”
Episode Two of No More No More Boys and Girls: Can Our Kids Go Gender Free? is on BBC Two at 9pm on 23 August.