This year the Royal Society has been marking its 350th anniversary. Among the most important figures in the history of British science are Henry Cavendish and Paul Dirac. In the 18th century Cavendish made major breakthroughs in the field of chemistry while in the 20th century Dirac revolutionised our understanding of quantum mechanics and the sub-atomic world. However, they have something else in common too - it's highly likely that they were both autistic. So what impact did the condition have on the lives of these two remarkable men? And could 21st century scientific advances ironically mean that another genius on the scale of Cavendish or Dirac is less likely to come along in the future?
Autism is a lifelong developmental disability that affects the way an individual interacts with others, make sense of the world and processes information. Today, more than half a million people in the UK are estimated to have autism (around one in 100 people) and it's more common in men than women. Whenever we meet a person, we can normally judge from their facial expression, body language and voice intonation what their mood is and respond appropriately. However, those with autism find it harder to read these signals. They usually have difficulty with communication, interpersonal skills and empathy. An autistic person may feel awkward and uncomfortable in everyday social situations and have problems expressing their emotions. They can have an excessively literal understanding of language and so may not understand jokes and sarcasm.
The term "autism" (which literally means "selfism") was first used by the psychiatrist Eugen Bleuler in 1911 to describe the social withdrawal and sense of detachment which affected many of his patients. In the early 20th century, clinicians who came into contact with autistic people often thought that their patients were experiencing schizophrenia until they realised that they were not displaying all the symptoms of that condition (people with autism do not suffer psychosis or a disintegration of personality). Research suggests autism is caused by a range of factors, both genetic and environmental.
As there are different degrees of autism, people commonly refer to the "autistic spectrum" and it can impact on people's lives in a myriad of different ways. A person with severe autism may have significant learning difficulties, may find it hard to acquire basic skills and need a lifetime of specialist support, while another person with the form of autism known as Asperger's Syndrome may be highly intelligent and able to perform a job successfully. One of the difficulties autism presents is that people with the condition don't look disabled, so they are often misunderstood.
Life can seem very confusing and disconcerting for someone with autism. Although autistic people can be highly creative and artistic, they may struggle with what's called "social imagination". They may find it hard to predict what might happen next, to prepare for change and plan for the future. They can have difficulty coping with new and unfamiliar situations. To try to reduce the unpredictability of the world, autistic people often love routines and may have difficulty adjusting if their routine is disrupted. They may want to dress the same kind of way, take the same route to work and eat the same food each day. Physical contact can be very intimidating so they may have difficulty forming relationships and choose to remain single.
People with autism may show a variety of unusual traits. For example, some are obsessed with clock-watching. If you tell them you will arrive at 3 pm, they will become very upset if you're only slightly late. An autistic child may spend hours arranging objects in neat rows, covering every room in the house with perfectly lined items. If someone attempts to move them, this will result in him throwing a tantrum.
Henry Cavendish displayed a number of characteristics associated with autism. As well as displaying an obsessive attention to detail and intense concentration, he was noted for his trouble relating to other people and spoke very hesitantly. One contemporary declared that "Cavendish probably uttered fewer words in the course of his life than any man who lived to four-score years".
Autistic people often choose to spend time on their own rather than with other people and Cavendish himself declared that he had a "singular love of solitariness". Apart from attending the weekly meetings of the Royal Society Club, Cavendish did his best to avoid company. Abnormally reclusive, he never established any close relationships outside his family and would only communicate with his servants in writing, ordering his dinner by putting a note on the hall table. He was particularly shy around women so, to avoid encountering his housekeeper, he added a back staircase to his house. His staff were told to keep out of sight if they wanted to avoid being dismissed.
Sometimes Cavendish literally ran away when a visitor arrived at his door. Those meeting him were advised not to make eye contact with him but to talk "as if to the air" and then wait for him to reply or walk away. He built his library four miles from his home to minimise the amount of contact he had with other people. His approach to life was so methodical that he never opened one of his books for his own use without entering it in the loan book. Even his principal heir Lord George Cavendish only saw him for a few minutes each year. Famous for his taciturn personality, one of his contemporaries described Henry Cavendish as the "coldest and most indifferent of mortals".
Cavendish showed little interest in having his research published or gaining recognition for his achievements. He didn't even communicate many of his findings to his fellow scientists. A number of his discoveries only became public knowledge when other scientists, such as James Clerk Maxwell, went through his papers many years after his death. If all his work had been published during his lifetime, his reputation and influence would have been even greater than it already is.
Similarly, Dirac was known for his extreme reticence, literal-mindedness, lack of empathy and rigid patterns of behaviour. He avoided company as much as possible, preferring to take solitary walks. An extreme introvert who rarely displayed any emotion, he is believed to have cried only once, when his friend Einstein died. He was prone to very long silences and his disinterest in small talk and social niceties was legendary. His Cambridge colleagues jokingly created a new unit called a Dirac and defined it as one word per hour. The eminent physicist Niels Bohr once complained, "This Dirac, he seems to know a lot of physics, but he never says anything."
Always an intensely shy man, Dirac almost turned down the Nobel Prize because he didn't want the publicity. He only accepted it when his colleagues pointed out to him that rejecting the prize would generate far more publicity than accepting it. When he arrived to collect the Nobel Prize, he caused confusion and panic by sitting quietly in the railway station's waiting room while the welcoming committee of grandees lined up on the platform became increasingly worried about his whereabouts.
It is possible that Dirac's behaviour was a reaction to his bleak, unhappy childhood. He once said, "I never knew love or affection when I was a child". Dirac's father, a Swiss immigrant, was an overly strict and authoritarian man who bullied his wife and insisted that Paul spoke only French at home even though they were living in England. Dirac's elder brother killed himself in 1925. Nevertheless, Paul Dirac displays all the classic signs of autism.
There are many anecdotes about Dirac's unconventional personality, which provide a revealing insight into his excessively logical and precise approach to the world around him. One year Dirac had to attend a conference in a castle that was believed to be haunted. When a guest mentioned that a ghost was meant to appear in one room at midnight, Dirac asked, "Is that midnight Greenwich Mean Time or midnight British Summer Time?"
The Russian physicist Peter Kapitza once lent Dirac a copy of Dostoevsky's Crime and Punishment. When Dirac returned the book, Kapitza asked him what he thought of it. Dirac's only comment on Dostoevsky's literary masterpiece was, "It is nice but in one of the chapters the author made a mistake. He describes the sun rising twice on the same day".
After one of his lectures, Dirac invited questions from his audience. One person commented, "Professor Dirac, I do not understand how you derived the formula on the top left side of the blackboard". Dirac snapped, "This is not a question. It is a statement. Next question, please." On another occasion, Dirac was attending a dinner party when a guest happened to remark that it was windy outside. Dirac left the table, walked over to the door, peered out, returned to his seat and replied that it was indeed windy.
Dirac, like many autistic people, had difficulty interpreting the thoughts and actions of those around him. He also struggled with the to-and-fro nature of conversations. At St John's College, he was once asked where he was going on holiday. After about 20 minutes, he replied, "Why do you want to know?"
He also liked to come up with theories for the most ordinary aspects of everyday life. At a party in Copenhagen, Dirac proposed a theory to determine the distance at which a woman's face looks its best. He argued that if a person were too far away, he or she would not be able to see the face at all while if a person were too close, the face would be distorted by the eye's small aperture and any blemishes would become exaggerated. This meant there must be an optimum distance for looking at a woman's face.
People with autism often have difficulty fitting in socially. In 1929, Dirac sailed to a conference in Japan with the scientist Werner Heisenberg. At that time both Heisenberg and Dirac were single men in their twenties but whereas Heisenberg liked to flirt with women, Dirac hated any form of socialising and did his best to avoid unnecessary contact with other people. One day on the ship, Dirac asked Heisenberg, "Why do you dance?". Heisenberg replied, "When there are nice girls, it is a pleasure." Dirac contemplated this concept for five minutes and then asked in consternation, "But, Heisenberg, how do you know beforehand that the girls are nice?"
Despite his uneasiness with company, Dirac married Margit, the sister of the Hungarian physicist Eugene Wigner, in 1937 and they remained together until he died. According to one account, somebody visiting Dirac, unaware of his marriage, showed surprise at encountering an attractive woman in the house. Dirac introduced Margit with the words, "This is Wigner's sister, who is now my wife".
Autistic people may appear insensitive because they can find it hard to recognize and respond to other people's feelings. Dirac was famous for his apparently emotionless responses to events. When Margit complained that he hadn't answered her questions about feelings in their love letters, he systematically compiled the questions into a grid and answered them one by one. During their 45-year marriage, his behaviour sometimes infuriated his wife. One day when Margit yelled at him, "What would you do if I left you?", Dirac thought for a while and then replied, "I'd say, 'Goodbye dear.'"
Dirac's autism never posed an obstacle to his scientific career. Indeed, it has been claimed his autistic traits were vital to his success as a physicist. His extraordinary ability to concentrate and focus on the task in hand, his adeptness at ordering scientific information in a systematic way, his visual imagination and his self-centredness all helped him in his career. In his diary, Dirac wrote that during his postgraduate years he spent all his time on research, only taking a break on Sundays for a long solitary walk. If Dirac hadn't been autistic his achievements may not have been so immense.
The same could easily be said about Cavendish. As a result of his autism, Cavendish devoted himself to his research with an enthusiasm that came close to obsession. His work was renowned for its range, thoroughness, precision and accuracy. He was always meticulous in his approach, often repeating an experiment numerous times.
Obviously, Cavendish and Dirac were exceptionally gifted scientists. But it is perfectly possible for many people with autism to lead a fulfilling life. Often people with Asperger's Syndrome can train themselves to make eye contact, smile, shake hands and to add animation to their voice when they meet someone. And autistic people may use certain tactics to help them cope with everyday life. Telephones can be particularly frightening - it's common for someone with Asperger's Syndrome to jump when a phone rings. But if they use caller ID, this reduces the fear by reducing the sense of the unknown.
Autism presents a challenge both to the person living with the condition and to their loved ones. Some families may find it difficult and embarrassing to explain an autistic relative's strange behaviour to their friends and acquaintances. Parents may receive disapproving looks from members of the public who assume that they simply have a very naughty, disobedient child. An autistic person may have no sense of danger so those close to them have to be permanently vigilant.
However, according to those with experience of living with an autistic person, the key step to take is to stop trying to make the autistic person more "normal". Instead of expecting the autistic person to speak in your language, you have to learn to speak in his. One family found they could communicate with their autistic member by using toys and puppets. They altered their tone of voice to one that made him feel more relaxed and put him at his ease. Now they have reached the point where they see his autism not as a condition but more as a facet of his personality.
A prenatal test for autism is not yet available but it soon could be. Already it is possible to use embryo selection during IVF to reject babies with autism genes. This could have the effect of preventing individuals like Henry Cavendish and Paul Dirac with brilliant scientific and mathematical skills from being born. Is this what we want to happen? If scientists do develop a test to detect autism in foetuses, and doctors advise mothers to consider termination of their pregnancy if their baby tests 'positive', what would society lose in reducing the number of children born with autism?
Few people would recognize the names of Paul Dirac and Henry Cavendish today. Outside the world of science they are little known. In this special year for science, it would be a fitting tribute to their achievements if we all set out not only to expand our knowledge of science but also to increase our understanding of autism.
In these early years of the 21st century we are beginning to see autism in a fresh light. We have begun to acknowledge that people with autism can have their own special abilities. Thanks to the exceptional skills autism gave Dirac and Cavendish, such as their capacity for deep concentration and the visualisation of numbers and patterns, they perceived things that even the best of their contemporaries were unable to comprehend. Above all, autism forces us to change our perceptions of what "normal" behaviour is. As Brian Cathcart observes: "That which made Dirac strange may also have given the world a genius". Instead of wanting to eliminate autism, perhaps we as a society need to learn to accept that there really is no such thing as "normal" behaviour.
The Strangest Man: The Hidden Life of Paul Dirac by Graham Farmelo
For general information about autism - National Autistic Society 
In this article, Victoria gives her personal views. These are not the views of the BBC.