Can IQ be linked to parenting? Harriet Swain asks Peter Hobson about some unsettling ideas in his latest book.

Peter Hobson is feeling self-conscious. You can tell. He flaps his arms around more when the camera is on him and wriggles when he says something that may be controversial. He is not used to giving interviews, he says, and wants to know how interesting I think he is likely to be, what I thought of his book, and, afterwards, how useful he has been.

His only other book was, as he puts it, "so dense and laden with references that only a few academic stalwarts managed to read it from cover to cover". This time he has decided "to go for it", not only writing a book - The Cradle of Thought - aimed at sharing his ideas with the general reader, but taking part in the accompanying publicity.

And go for it he has, presenting in clear terms a theory about thinking that has implications for the origins of language, for what it means to be human and - the aspect most likely to disturb the general public he wants to reach - for parenting.

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"Do not, whatever you do, say that I think bad parenting creates children with low IQs," he warns. He does not. But he does say in the book that his ultimate aim is "to understand how nature dovetails the human infant's innate capacity for social engagement with what a care-giver provides, and thereby creates an interpersonal cradle for the growth of symbolic thinking".

He describes an experiment involving three-year-olds and their mothers that showed that the children of secure mothers - those able to provide coherent accounts of their own early relationships - scored higher in IQ tests than those of insecure mothers. And he states that "the quality of a mother's engagement with her child affects the child's ability or inclination to engage with other people's engagement with the world".

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This may not add up to "bad parenting equals low infant intelligence", but it does raise disturbing questions about just what effect parents who engage poorly with their children may be having. Hobson suspects that in the long term, IQ is not that affected by such parental failing. More susceptible, in his view, is the child's "capacity to maintain balanced, rational thinking under stress".

These are just a couple of the tricky issues that arise from the central thesis of the book - that the emotional interchanges that babies experience with people around them are the basis for how they learn to think. Through such interchanges they develop a sense of other people as separate from themselves, with separate points of view. They therefore develop a sense of self. These two realisations allow them to use symbols (language) because they know that what has meaning for them will have meaning for others.

But Hobson goes beyond babies. For him, this explanation of how children learn to think also helps to explain the evolution of human thought. "Our human pre-sapiens ancestors differed from their chimp-like peers in the primate world by virtue of their deeper connectedness with each other," he writes. "It was this that gave them thought and the leg-up into language."

He believes that it was through minute changes in emotional interchanges and relationships that we evolved into creatures able to think and to communicate, just as it is through such small changes over the first 18 months of life that a baby develops the same capacities.

One of the ways he has arrived at this theory is by looking at what happens when this system breaks down. Much of Hobson's thinking has been influenced by his work with autistic children. His first "dense" book was called Autism and the Development of Mind . These children, he argues, do not have the same sense of people as the rest of us. For them, the universal body language that mentally connects us with others does not seem to work. Nor do they seem to relate to the world through others, as most other people do. He suggests that it is for these reasons that many children with autism are not self-conscious and that many are unable to use much language.

Hobson believes "the roots of autism are to be found in what fails to happen between people". It is an example of what can happen when there is a severe problem with early interpersonal relationships." "The combined operation of infant-in-relation-to-care-giver is a motive force in development," he writes. "When it does not exist, and the motive force is lacking, the whole of mental development is terribly compromised. At the extreme, autism results."

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So bad parenting can cause autism? Again he insists this is the wrong equation. For one thing, a baby's propensity to relate to other people and to read how other people see the world is so strongly inbuilt that it usually takes some kind of brain damage caused by infection or a genetic defect to create serious enough barriers to social engagement for autism to exist. But Hobson concedes that, in extreme cases, autism may be induced not so much by bad parenting as by no parenting.

He describes a study involving children who had been placed in Romanian orphanages when they were a few months old, under deeply deprived conditions, and who were later adopted into families in the United Kingdom. Of the 111 children studied, about one in 16 showed characteristics closely resembling autism, while a further one in 16 showed milder autistic characteristics. The usual incidence of autism is about one in 1,000. "It appears that autism, or something very like it, can arise as the result of severe privation," he concludes.

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But there are other reasons for things failing to happen between people. Hobson describes conducting an experiment on children born blind that found that ten of the 24 children studied satisfied the clinical criteria for autism - although they tended to be autistic in a slightly unusual way. They were often less impaired in emotional expressions and had better relations with people. He suggests that this is because their autism was the result of an inability to see rather than an inability to perceive how other people related to the world.

He insists there are practical lessons to be drawn from what he has found. "One has to be clear about the limits of teaching things to autistic children," he says. Instead, he believes the focus should be on trying, by whatever means possible - music perhaps - to promote these children's engagement with other people. Also, it is important to recognise different kinds of autism. He suggests that children whose autism is linked to congenital blindness are most likely to benefit from intervention.

He refuses to engage with the current controversy over whether the measles, mumps and rubella jab causes autism. "I am like other parents (he has three children) anxious about the possibility but I know the medical establishment thinks a link is unlikely," he says. "I have nothing interesting to say about it." This is perhaps because, despite his medical background, his interest in autism is part of a wider interest in interpersonal relations.

His father, Peter, was a Jungian psychotherapist and Hobson first studied medicine and then psychology at Cambridge, where he developed an interest in psychotherapy and philosophy of the mind. He went on to work as a psychiatrist at the Maudesley Hospital, where he made his first visit to a school for autistic children. He then began looking into psychoanalysis, while simultaneously completing a PhD in experimental psychology. He maintains the triple interests of psychiatrist, psychologist and psychoanalyst and has brought them together in his new book, using clinical studies, experiments and examples drawn from therapy sessions to explore his themes.

Through this multiple approach, Hobson says he has experienced the prejudices of one discipline towards another. But he has no time for such divisions. He argues that we are social creatures, who relate to the world through other people and who, through others, develop an insight into ourselves.

The Cradle of Thought : Exploring the Origins of Thinking is published today by Macmillan, ?20.00.

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