It was back in the 1970s that feminist educational researchers first studied the implications of the tendency for girls to play with dolls, and for boys to play with cars. They found that the way girls played developed their communication skills and emotional literacy, while boys' toys encouraged them to grow up with better technical knowledge.

The arrival of the national curriculum in the 1980s, and the consequent improvements in the academic achievements of girls, rendered the theories linking toys and potential for learning as unfashionable, and perhaps irrelevant.

But new research suggests that the issue should be revisited because, it seems, there has never been greater gender stereotyping in the production and marketing of toys than now.

"People might think that toys are more androgynous these days, but go into any toy shop and you will find separate aisles, and even separate floors, for girls and boys," says Becky Francis, professor of education at Roehampton University. "The packaging is geared towards either boys or girls by colour, wording and the images portrayed on them. This creates the impression that certain toys are just for boys and others just for girls, and so some toys are completely out of bounds."

Francis's study, Gender, Toys and Learning, funded by the Froebel Educational Institute, is thought to be the first in more than 20 years examining the educational value of toys and their impact on learning. Francis asked the parents of more than 60 three- to five-year-olds what they perceived to be their child's favourite toy. (This age group was chosen because it is when children start being aware of gender differentiation in themselves, and in the toys they play with.)

She found that while parental choices for boys were characterised by toys that involved action, construction and machinery, there was a tendency to steer girls towards dolls and perceived "feminine" interests, such as hairdressing.

"The very clear message seems to be that boys should be making things, using their hands and solving problems, and girls should be caring and nurturing," she says. "It is likely that many of the boys in the study sleep with a teddy, but this was not noted by parents as a favourite toy."

The parental preferences revealed in Francis's study come as no surprise to Diane Daniels, who runs a nursery for three- and four-year-olds in Sheerness, Kent. "Even very young children come to us with preconceived stereotyped ideas about what they should be playing with, and certainly we know of dads who would not dream of their sons dressing up because they think this is something girls do," Daniels says. "They want them to play with cars and other masculine toys.

"We spent a lot of time making sure our pupils do activities that involve a full range of toys, regardless of whether they are for boys or girls, but it can be hard. It doesn't always work as we would wish because parents are the first educators and so have already exerted a lot of influence over the way their children play.

"It is noticeable that girls are terribly 'pink' at the moment. Everything geared towards them seems to be pink."

These early play preferences may not only be the result of socialisation and marketing, however. A 2005 study looking at the play of young primates, by psychologist Professor Melissa Hines of Cambridge University, found that when offered a variety of toys, female monkeys tended to gravitate towards dolls and soft toys, while males chose toy cars.

"There are certainly genetic factors at work here, and we believe that children's play preferences may be determined even pre-birth," Hines says. "The levels of male and female hormones in an expectant mother may result in children being born predisposed to certain play preferences."

It is the impact of gender stereotypical play on children's future subject preferences and job prospects that concerns Francis most. "While girls have largely caught up with boys when it comes to achievement in maths and science, they are still less likely to be high achievers in these subjects or to study them beyond GCSE," she says. "At the same time, they outperform boys in literacy and humanities subjects. Early play, I believe, has a crucial impact on these trends."

Drawing on her findings, Francis purchased several of the items that her study found were most popular with the age group, and analysed them in detail for their potential for learning. She found that, at best, girls' toys - dolls and teddy bears - made for imaginative and creative play. Only Baby Annabell, the lifelike doll, offered any kind of learning experience.

"Of the girls' choices," Francis says, "the learning potential was limited, and there was little that could be related to skills development that relates to the curriculum, although Baby Annabell provides well-developed information on the needs of a baby and how to meet those needs."

The play choices for boys, however, were far more diverse and included cars, models of action heroes and popular television characters. And while dolls and teddy bears were sold with little external packaging, that covering boys' toys was "busy", denoting action and speed with strong colours and wording that evoked excitement and machismo. Instructions for use were often technical, requiring boys to draw on their literacy skills, and provided knowledge and activities around construction and technology.

"Boys are propelled into a world of action as well as technology, and their play is designed to be exciting and stimulating," Francis says.

We tested her theory about the marketing and packaging of toys at Hamleys toy shop in London's Regent Street. The store directory on entry was helpfully colour-coded - floor 3, highlighted in pink, was for girls, while floor 5, blue, was for boys.

We stopped first to look at the pre-school ranges. Toys aimed at babies and very small children had few, if any, gender-specific markings, and were produced in a range of soft, pastel-coloured fabrics and materials to appeal to both sexes.

This changes, however, in toys aimed at children aged 18 months onwards. Vast swaths of blue-coloured boxes on the display shelves left shoppers in no doubt that these were aimed at boys.

But it was the toys for very young girls that were perhaps the most intriguing. Even Dora the Explorer, the feisty adventurer who is used to crossing forests and crocodile-infested lakes, could not escape being stereotyped. In one boxed set she is presented in a nurturing role, as an "older sister" clutching a baby's feeding bottle, and with two younger siblings in tow.

"This is a classic example of how the toy manifestation of the cartoon character is more gender-stereotyped than the cartoon or show in which they appear," Francis says. "Boys who enjoy Dora as a cartoon are unlikely to want to play with her mother-like doll.

"Toy companies are aware of gendered consumer preferences, and develop and market their toys to these trends, so closing down broader options and perpetuating the gendered toy market."

As might be expected, the girls' floor at Hamleys is an array of pink packaging and cuddly toys, with a dressing-up section of fairy costumes and sparkly outfits. There is little to encourage boys to explore here.

On the 4th floor, designated as being for "hobbies" and packed with construction kits, models of action heroes and radio-controlled cars, we ask a shop assistant to point us to the resources for girls. "Like what?" he asks - which seems to say it all - before sending us back to the third floor with an assurance that that is where we'll find "arts and crafts stuff".

"Toy shops are almost entirely for boys," Francis says. "There is little for girls, and even less that can be considered to have educational value."

Matt Webb, head of marketing at Hamleys, says children are savvy consumers and there is a tendency for boys and girls to gender stereotype themselves in their play, often through peer pressure.

"When it comes to packaging and merchandising, this is really done for the convenience of parents and children, so they know where to go to find what they are looking for," he says. "We stock thousands of items, so it makes sense to give people some direction as to where they can find what they want, and to package them appropriately. This isn't intended in any way to say to people, 'This toy isn't for you.' There is nothing to stop boys and girls playing with each other's toys, and this is something we would encourage."

But Sue Palmer, an early years literacy consultant and author of Toxic Childhood: How the Modern World is Damaging Our Children and What We Can Do About It, says toy manufacturers are cornering children into gender roles from a very early age. "Pink is absolutely endemic for girls," she says. "Big business is sending out a message to girls and boys about how they should behave. Instead of capitalising on the best characteristics of toys for boys and girls, and encouraging children to explore with both, we are all quietly colluding by buying these items."

Professor Jeffrey Goldstein, chair of the National Toy Council, disagrees that it is the fault of manufacturers and marketing. The organisation monitors trends in toy manufacture and use. "Parents tend to have traditional attitudes about the gender roles of their children," he says, "and where buying toys is concerned, they tread the path of least resistance.

"Of course, it is preferable that children are exposed to a wide range of play experiences, because this opens up the world around them, but this is not something we can control or legislate for."

Several toy manufacturers, including Tomy and Fisher Price, failed to return our calls on the issue.

Melissa Wallace, PR and promotions manager at Lego, admits its core market is currently boys aged five to nine. However, she says, Lego produces a range for girls, called Belville, with sets containing themes such as "horse jumping" and "royal summer palace", as well as offering much to interest them in its unisex range.

"Our toys stimulate creativity in both boys and girls, and help to develop hand-eye coordination and motor skills, colour recognition, patience and self-esteem," says Wallace."Girls enjoy playing with Lego, but in a different way to boys."

She adds that Lego will be exploring new avenues and markets next year - "of which girls may be one".

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