There have even been some cases where synaesthesia occurs after an injury to the brain.

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As president of the UK Synaesthesia Association he meets many people with these types of abilities.

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And Mr Wannerton's relatively rare form is known as word-taste or lexical gustatory synaesthesia.

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Synaesthesia can come in many forms as the different senses mix and melt together.

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It was in this context that Eisenstein developed his theories of montage, typage and synaesthesia.

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The most common type is grapheme-colour synaesthesia where people perceive words, letters and numbers as distinct colours.

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The tendency to have synaesthesia runs in families, though relatives will often have different types of it.

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But there is still a long way to go in understanding synaesthesia, particularly in identifying genes responsible for the condition, researchers say.

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And research as early as 1963 suggests synaesthesia can be induced by drugs such as LSD - opening up the possibility the condition may be in part due to an imbalance of chemicals in the brain.

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