even dislike of the person they are speaking to, the reverse is true, and differences are sought. This mechanism also extends to language, as described in the Communication Accommodation Theory. Some multilinguals use code-switching, which involves swapping between languages. In many cases, code-switching allows speakers to participate in more than one cultural group or environment. Code-switching may also function as a strategy where proficiency is lacking. Such strategies are common if the vocabulary of one of the languages is not very elaborated for certain fields, or if the speakers have not developed proficiency in certain lexical domains, as in the case of immigrant languages. This code-switching appears in many forms. If a speaker has a positive attitude towards both languages and towards code-switching, many switches can be found, even within the same sentence. If however, the speaker is reluctant to use code-switching, as in the case of a lack of proficiency, he might knowingly or unknowingly try to camouflage his attempt by converting elements of one language into elements of the other language through calquing. This results in speakers using words like courrier noir (literally mail that is black) in French, instead of the proper word for blackmail, chantage. Sometimes a pidgin language may develop. A pidgin language is a fusion of two languages that is mutually understandable for both speakers. Some pidgin languages develop into real languages (such as Papiamento in Curaçao or Singlish in Singapore) while others remain as slangs or jargons (such as Helsinki slang, which is more or less mutually intelligible both in Finnish and Swedish). In other cases, prolonged influence of languages on each other may have the effect of changing one or both to the point where it may be considered that a new language is born. For example, many linguists believe that the Occitan language and the Catalan language were formed because of a population speaking a single Occitano-Romance language was divided into political spheres of influence of France and Spain, respectively. Yiddish is a complex blend of Middle High German with Hebrew and borrowings from Slavic languages. Bilingual interaction can even take place without the speaker switching. In certain areas, it is not uncommon for speakers to use a different language within the same conversation. This phenomenon is found, amongst other places, in Scandinavia. Most speakers of Swedish, Norwegian and Danish can communicate with each other speaking their respective languages, while few