Communication is probably one of the most important of all human behaviours. Our use of language may be private - we can think to ourselves in words or write diaries that are meant to be seen by no one but ourselves - but language certainly evolved through social contacts among our early ancestors. Speaking and writing are clearly social behaviours: we learn these skills from other people and use them to communicate with them. An effective language system also tends to abide by certain rules. Although an exact definition is difficult to pin down, language can be characterised as a system of visual and/or vocal symbols which have meaning to the user and to the recipient. There are thought to be around 6000 distinct languages in the world. The world's largest language is said to be Chinese - it has more native speakers than any other - followed closely by English, Hindi/Urdu, Spanish and Arabic. The most popular foreign language is usually claimed (Smith, 2003) to be English.