Are you a man or a woman? I ask because your sex will determine your likelihood of pursuing certain routes in life, and these likelihoods are different for each sex.

Four-fifths of UK politicians are male, only one eighth of British FTSE 100 directorships are held by women, and most nurses are female. Men are more likely to start a business and UK women get paid, on average, 15.5% less than UK men. If you're female, you're more likely to spend time with your kids. If you're male, you're more likely to end up in prison.

I bet you're thinking: So what? Who cares what other people do? You're right. Individuals are free to pursue what they want - there aren't laws blocking us anymore, at least in the Western world. Nowadays, women don't need their husband's permission to get a mortgage. Nowadays, women can vote. Nowadays, school leavers aren't given separate careers forms with different job possibilities for boys versus girls.

But are we, as individuals, really free?

The overt prohibitions of the past have turned into subtle restrictions of the present. Social gender pressures are still there but now to give in to them is voluntary. Sounds better? Only thing is that social pressures are often the strongest pressures of all.

Marketing exploits gender stereotypes, channelling utterly different products and lifestyles to boys versus girls, men versus women, tapping into social norms, reinforcing differences and promoting the development of different skills, interests and goals. In society generally, women and girls and encouraged to be and rewarded for being pretty, polite and passive, while boys and men must be macho, protective and strong.

Parents, teachers, peer groups and employers buy into this without even realising it, and failure to conform results in ridicule and ostracism. The more we do something, the better we get. So before know it, girls and boys en masse are enjoying and pursuing divergent activities and roles in society.

I still know what you're thinking. But men and women are naturally different!

I encounter this line from blog commenters, journalists and critics. A couple of years ago, I began to question its truth. I read books and articles. For months, I studied the evidence and its implications, and, when I emerged from my review period, I was excited and liberated. My conclusion: there is no universal scientific consensus that men and women are born with different cognitive (thinking and reasoning) skills. Conversely and worryingly, what we do with our brain as we progress through life is far more likely to change its structure and function.

At the end of December 2011, I successfully campaigned to remove the gender-specific labels from Hamleys toyshop, arguing that the separation restricted parent's and children's choices, interests and aspirations. The story received explosive and substantial media coverage all over the world. The reaction, a potent mixture of extreme support and passionate anger, showed how emotional this topic is; that it resonates with people's relationship with their identities - or their unrest at being forced into identities they don't want.

Many people told me they hadn't considered the issue before, or they had assumed the sexes were born different. Some who had vehemently opposed me in the past changed their minds and became advocates. Many were grateful that the topic is in the limelight and open for debate, progress and change.

My new project builds on this. Breakthrough: The Gender Stereotypes Project is a groundbreaking schools programme that kickstarts the gender stereotypes debate among children, their parents and their teachers. I am working with Laura Kirsop, inspiring and dynamic year 5 teacher at Soho Parish School in central London, to run a two-week lesson programme, beginning on Monday, with the aim of exploring the influence gender stereotypes. It follows concerns from pupils and parents that stereotyping may be stopping children from fulfilling their true potential.

Breakthrough's aims are to benefit both boys and girls, to encourage debate, rather than pushing children into thinking a certain way, and to cover all aspects of gender stereotype awareness - interests, marketing, aspirations, personality strengths and skills. It's a project about individual freedom and tolerance, acceptance and respect.

So what's next? Following the pilot, the plan is to roll this out so more children can benefit. The demand is there - I am receiving requests from parents, governors, teachers and potential partners, and ideas to develop this programme to cover more age groups with more material.

People often ask me: I know gender stereotypes are affecting my kids - what can we do about it?

I say: you can either lobby for laws or practices to change or you can shift a culture at its core. Changing a culture from the inside out is Breakthrough's mission. If the tide is there, it will turn, and we may see a new horizon before us.

Follow Dr Laura Nelson on Twitter: www.twitter.com/DrLauraNelson