It's a windswept, freezing January afternoon on a remote beach in Scotland, and I'm watching four horses, each with a child on its back, plodding across the pebbles. Eight-year-old Rowan Isaacson is standing beside me on the beach. Like the other children, he is autistic: unlike them, he can carry on a conversation, speaks clearly and is toilet-trained – but only since 2007. According to Rowan's father, Rupert, his extraordinary "recovery" from some of the most difficult aspects of autism came about through his love of horses – a love affair that culminated in a month-long, adventure-packed trip to Mongolia.
It's a compelling tale of the lengths to which one couple are prepared to go to make their child better. Not surprisingly, the phenomenon of a little boy with autism, whose symptoms melted away once he climbed on to a horse, delighted the media – and the resulting book, The Horse Boy, made it on to the New York Times bestseller list. Almost inevitably, there are now plans for a feature film.
But does their experience have anything to offer other families? Here on this beach, Rupert and Rowan are trying to prove it does. They are over in Britain from their home in Texas (Rupert is British, but his wife, Kristin Neff, is American, and the couple have lived there for many years) to run what they are calling a horse boy camp for other families who, like them, live with autism every day.
It was in 2004 that Rupert, who has worked as a horse trainer, first thought the animals might hold an answer to Rowan's condition. One of his many sadnesses after the autism diagnosis was that he would never be able to share his passion for horses with his son. Then, one day, something extraordinary happened. Father and son were walking near their home in Texas when, in one of those stomach-lurching moments every parent dreads, Rowan ran off and darted through a fence into a field of horses, throwing himself right in front of a large and grumpy-looking mare. The horse could have trampled him to death. Instead, as the little boy chuckled up at her, the horse dipped its head in a sign of equine submission. "What I realised," he says, "was that my son had a kind of direct line to the horse. He was on a wavelength with her, in a way that most human beings aren't on a wavelength with animals."
Although he had thought Rowan would never be able to ride, Rupert decided to take the risk: he saddled the mare, Betsy, and asked his son whether he wanted to get up. "I wasn't expecting a response: but for the first time ever, he gave me an answer to a question. 'Up,' he said. And off we went."
Before long, Rupert was spending every minute on Betsy's back, holding a now speaking Rowan in front of him in the saddle. The progress was palpable, but complex: Rowan was still unable to say yes or no, but could now put together his first sentence: "Want go ride Betsy." With each glimpse of improvement, Rupert and Kristin longed for a major breakthrough. "Not a cure," says Rupert, "because with autism there is no cure … but a healing."
Not long before, Rupert – a travel writer – had attended a gathering of traditional healers, tribal herbalists and shamans in California, and had taken Kristin and Rowan along. Some of the healers laid their hands on Rowan, and the couple had noticed an improvement in their son's speech and behaviour afterwards. That experience, combined with the horseriding advances, led Rupert to the extraordinary idea of taking his wife and son to Outer Mongolia, which some claim is the original home of the horse.
The family spent a month in Mongolia in 2007, riding across the steppe towards a sacred lake, then on to see the country's most renowned shaman, an old man called Ghoste who lives in a tepee. Along the way there were all sorts of adventures: encounters with other healers, a day-long healing session on a holy mountain. The trip was often arduous, and at times chaotic, and punctuated with the bizarre – as well as having to drink copious amounts of mare's milk curd at various traditional gatherings, there was also an occasion when the bowl of soup proffered contained reindeer faeces. "We drank it," remembers Rupert. "It was utterly disgusting!"
But the Mongolian trip brought plenty of what his parents see as genuine breakthroughs for Rowan. He made his first real friend (a six-year-old boy called Tomoo), learned to talk in sentences and, by the time they came home, he was at last toilet-trained and had stopped throwing the wild temper tantrums that had been a feature of family life up to a dozen times a day. "It was amazing," says Rupert. "We had returned home with a completely different child."
It is a remarkable story that has led to lavish publishing deals and Hollywood beckoning. Rupert reportedly got a $1m (£610,000) advance from the publisher Little, Brown, even before the family went to Mongolia in 2007.
But is it too good to be true? Some experts have expressed scepticism. Simon Baron-Cohen, professor of developmental psychopathology at Cambridge University and Britain's foremost autism specialist, says he hasn't read Rupert's book, nor seen the documentary film the family shot in Mongolia. It's surprising, especially as the book describes a visit the Isaacsons made to see him. They agreed to differ on the reasons behind the rise in cases of autism (Baron-Cohen thinks it's the result of increased diagnosis, whereas the Isaacsons believe it's more likely to be linked to environmental pollution), but agreed on one thing, which is that autism may be more about personality than a pathological problem.
Other experts are voicing concerns. Paul Offit, of the Children's Hospital of Philadelphia, author of Autism's False Prophets, has said anecdotal examples of recovery such as The Horse Boy could give parents "false hope" and lead them to spend a lot of money on an experience that might do nothing to help. (A four-day stay at a horse boy camp costs £850 per family, although some places are subsidised.)
Other experts, such as Bernard Fleming, of Research Autism, point out that the main problem with The Horse Boy is that it's anecdotal. "The problem is that we've not yet got any high-quality research," says Fleming. But he wouldn't want to dismiss the possibility of horses being helpful – one of the projects the charity is funding is looking into whether dogs can help people with autism. "It could be that a child could be helped as much by the experience of being away on a trip with their family, as by the presence of an animal," he says.
Rupert's contention, gleaned partly from his experiences with Rowan and partly from interviews with autism specialists, is that what horses have to offer is to do with the repetitive, rhythmic pattern of horseriding, which seems to open up the learning receptors in the brain.
Another element of the camp is to recreate in microcosm the journey the Isaacsons made in Mongolia. "One of the most important things, apart from the riding and the shamans, was being close to nature," says Rupert. "And that's hugely important because man-made environments are much harder places to be for autistic people. Fluorescent strip lighting is a problem for them, and so is machine noise – they throw the wrong switches in their brains and cause a lot of pain and distress. Being close to nature is far less likely to cause those problems – it's a much healthier, easier place to be."
The horse boy camp, which also features a Californian healer called Jill who lays hands on the children, seems steeped in new ageism – but, while Rupert admits he's an ageing hippy whose first loves were "sex and drugs and rock'n'roll", he claims, all the same, that he hasn't got a new age bone in his body. The only thing he's interested in, he says, is what seems to work.
Perhaps his most important message, and one certainly embraced eagerly by the other parents at the camp, is the idea that people with autism aren't just people with problems but people with gifts and talents who can challenge the "normal" way of doing things in a positive way. "Is autism a tragedy or is it a different skills set?" asks Rupert. "Should we be trying to turn autistic children into 'normal' kids, or should we be doing something different, which is teaching the survival skills to swim in our culture?
"People with autism have advantages over the rest of us – they have an extraordinary ability to focus, a lack of ego, a drive that's not distracted by other stuff. Being with Rowan, I sometimes think, who's the talented person here? When we're training horses, if Rowan is around they'll behave better and learn more quickly – so who is helping who?"
Nor does Rupert believe that horses have some sort of magical quality – they might have in Rowan's case, but not with other children. The most important thing he's saying, and the thing the other parents on the camp seem to most value about him, is to believe in your kids. Believe that there's a way forward and you will find it, and don't assume that autism has to be the end of everything. For the Isaacsons, after all, it has been the start of a new, exciting way of life.
"What's really inspiring about being here," says Rowen Saunders, who is at the camp with her three-and-a-half year old son, Oak, "is that we're all helping one another and we all understand what it is to have a child with autism."
"What the camp has given us is an opportunity to have a good time, and to do that among people for whom autism is a normal part of life. And we're finding that in this place where there's so much positivity, huge strides forward can happen, especially in terms of our children being able to communicate and socialise. That's important because it's going to help them to be less frustrated and more fulfilled," she says.
Despite sub-zero temperatures, each day involves several hours on horseback for the children. So far, the parents seem pleased: Zabedah Ferrari, is delighted with her daughter's progress – Natasha, 13, is grinning broadly beneath her hard hat – and says she is less agitated than she has been for a long time.
Rowen Saunders, too, has seen "really striking improvements" in Oak's behaviour. "It's only been 48 hours, but he's saying more words, he lets us brush his hair and he's been kissing us goodbye. That might not sound much to you, but let me tell you – for a parent of a child with autism these are major miracles."
The Horse Boy by Rupert Isaacson is published by Penguin, £7.99. To order a copy for £7.99 with free UK p&p, go to guardian.co.uk/bookshop or call 0330 333 6846. For more information, go to worldwild.co.uk/horseboy.html