One of the biggest mysteries of science is how the human brain functions. Scientists are now tuning into the abilities of a group of people with an unusual condition to help unravel how our brains are networked. Enter the fascinating world of the woman who tastes words.

"My own name tastes of satsumas, and of' tastes of the squidgy bit in the middle of pavlovas," Lucy Shaw explains when I meet her in comfortable Oxford town house. The seeming pretension of what she is telling does not escape the notice of this quiet, well-spoken mother of two, and she smiles wryly as she talks. Tempting though it is to dismiss Lucy's claim as fanciful and ridiculous, she is simply trying to explain how she experiences the world around her. She has synaesthesia - a condition that is the cause of much excitement among psychologists and neuroscientists.

While most of us learn about our surroundings through five senses, people with synaesthesia go one better. During very early life, two or more areas of their brain responsible for different senses become inextricably linked. The result of this linkage is that synaesthetes may perceive words as having colour, smells as having shapes or voices as having tastes.

m/f Synaesthesia can take many forms but Lucy has the relatively rare lexical-gustatory type. For her, words have a distinct, specific (not just roast beef, say, but roast beef with onion gravy) and constant taste.

If you're still struggling to understand what it's like to have synaesthesia, you're not alone. Although modern scientists have known about this condition since the late 19th century, synaesthetes have often been dismissed as over-imaginative or liars and have had to contend with mockery and distaste. Lucy can relate to this. "As a child, I assumed that everybody had it. I would say let's play what flavours different numbers have'. But my mother actually got a bit cross, so I just didn't talk about it for years and years." Only when a university friend described to her the experiences of a synaesthetic artist that she had been studying did Lucy realise that she may have a recognised condition and began investigating. Eventually, she found a newspaper article on another lexical-gustatory synaesthete and set up a correspondence with him. "It was so exciting to find someone else like me."

m/f Charlotte Hanson Synaesthesia 3 Lucy's synaesthesia affects every aspect of her life. "It can be a bit distracting. We once had a dinner party where, after the meal, one of the guests was talking and talking. Her voice had a flavour and the more she talked the more full I felt. I had to leave the room!" Her husband, although supportive, is still slightly puzzled by Lucy's synaesthesia, and he was, unsurprisingly, somewhat bemused that Lucy's word-taste connections influenced the choice of names for their two children. "I couldn't have a name that didn't taste right," she says. I can see where her husband was coming from.

However weird synaesthesia may seem, Lucy is adamant that it makes life very interesting, and her eyes light up when she discusses her condition. She is unable to read a famous series of detective novels because the taste of the stories is overwhelmingly greasy. It can also be great fun. "My husband is a philosopher and once, on holiday, I started reading one of his books by an eminent Oxford don. It tasted so fantastically of chocolate that I read quite a lot without taking in a single word. I could taste chocolate clairs, chocolate truffles - it was delicious!"

Scientists believe that synaesthesia may be associated with enhanced creativity, and it must be said that Lucy bears this out. As well as being interested in art and music, she is a talented professional cake baker and decorator. In front of her sits a magnificent purple and gold creation, ready to be collected for a birthday party. "Cooking comes easily to me because I could always remember the tastes very well. I can easily conjure up a taste that I've tried before."

m/f Charlotte Hanson Synaesthesia 4 There has been an explosion of interest in synaesthesia in the last ten years and now, people with the condition are helping psychologists and neuroscientists to unravel the mysteries of cognition. Lucy has taken part in tests for researchers who are studying the relationship between synaesthesia and cognition at University College London. Dr Jamie Ward, a cognitive neuroscientist and head of the Synaesthesia Research Group at UCL, explains that Lucy is not simply imagining the tastes that she associates with particular words. "Synaesthesia is a sensory phenomenon. In other words, synaesthetes are actually perceiving a taste in response to language." By understanding how the brain is wired in people with synaesthesia, Dr Ward and fellow researchers hope to determine the organisation and function of the human brain. Some scientists even believe that synaesthesia can help to explain the emergence of abstract thought, metaphor and language.

It has been a fascinating conversation, but as I leave I realise that I still have no real inkling of Lucy's world of tasty words. But however strange her world seems to an outsider, there's no doubt that it's an immensely enriched, fun and fulfilling one.