When I was very young, I thought I knew how men and women should behave: men were breadwinners and women housewives. But already the world was changing.

Now, 70 per cent of women with children have paid work, and men are taking more responsibility for housework. A survey we carried out for the Child of Our Time series showed most of our parents believe traditional gender roles are now almost irrelevant.

At the same time, we talked with their children and discovered something disturbing. The children were busy constructing new gender roles, influenced less by tradition, parents and school than by the outside world. So, are we really bridging the divide of the sexes? Or, in a culture dominated by marketing, media, and materialism, are our kids giving a different message?

The power of marketing on gender identity is illustrated by an experiment we carried out with the Child of Our Time children, now seven years old - we are tracking 25 millennium children from birth to adulthood. We filled bottles with the same lemonade. One set we packaged as “Rocket Pop” with blue labels, and the other as “Princess Pop” with pink ones.

First, we asked the children which they liked the look of and - no surprise - the girls preferred the pink and the boys, blue. We then asked them to compare the taste of the drinks. The boys told us that “Rocket Pop has more fizz”, and “It’s better because it’s more flat”. Or, as one budding scientist put it: “It’s got more flavour because it’s got the least amount of water.” Then, the girls: “The blue one is a bit more dark and I don’t like it.”

We realised almost all our children believed the two identical drinks had different tastes, and they preferred the taste of the one aimed at them. The fact that the colours and design of the packaging affect their judgement attests to the power of marketing, both to deceive and drive a profitable wedge between the sexes.

This is where the media comes in. Children’s television is generally benign, but children are bombarded with much more.

Advertisements, music, magazines, and many TV stations live off a diet of sex, celebrity, money, and beauty. Young children are more impressionable than their elders. They are trusting, and highly attuned to social nuances because they need to feel accepted. It is not surprising that they soak up messages crafted to seduce the population for the benefit of the market.

Last year, the National Consumer Council (NCC) published a sobering study of children and materialism in the UK. They found that almost half the children polled in deprived areas would rather spend their time buying things than doing almost anything else.

Other studies show boys are the more materialistic sex, a finding corroborated when we asked the Child of Our Time children about the qualities they most admired. While girls wanted to be kind and healthy, the boys chose wealth, telling us: “Money is more important than anything”, and “I’d like to be rich and buy what I want”.

One might think the desire to be rich would spur boys to get educated, but it doesn’t appear to. Some of the able boys in our cohort told us: “Clever is so boring.” They felt cleverness was not cool; influenced, perhaps, by a celebrity culture that underestimates the hard graft needed to get there.

That may go some way to help explain why boys are falling even further behind girls in school. Again, children split along gender lines, for our seven-year-old girls told us: “If you are clever, everybody likes you more”, and “Clever means that you know what to do quite a lot of the time”. Girls seem to expect to do well in education, and often do so.

Even so, girls’ self-esteem is also under threat. The NCC study demonstrated how the media can magnify materialism to the point where it can substantially damage childrens’ self-esteem by making them feel inadequate. Girls respond by becoming increasingly perfectionist about their school work and their weight. Oliver James, the study’s author, told me that the rates of depression and anxiety among girls from high-income families had increased from 24 to 38 per cent in just 12 years. It is a high price to pay for having it all.

Children aged from seven to 11 make up an increasingly lucrative market, worth almost pound;20 million a year. They are much more susceptible to marketing than adults. Disadvantaged kids are even more materialistic than richer children, adopting brands that give them kudos and a sense of belonging.

Looking at a film of the Child of Our Time children at school one day, I noticed that the most animated conversation in the playground was generated by 10 of the seven-year-olds, bragging about which console they had, and whose was best.

The tragedy is that both girls and boys are being manipulated into believing not only that they are divided from each other, but also that they are inadequate; a dangerous state, which can damage their self-belief. As Henry Ford, the industrialist, pointed out: “Whether you think you can, or think you can’t, you’re probably right.”

Confidence makes all the difference to a life. Our children get affection and encouragement from parents and teachers. Don’t they deserve the same from the world outside?

- ‘Child of Our Time: Early Learning’ by Tessa Livingstone is published by Transworld. The ‘Child of Our Time’ series is on BBC1 on Wednesdays at 8pm.

Dr Tessa Livingstone, Author and executive producer of the BBC series ‘Child of Our Time’.