http://cordis.europa.eu/fetch?CALLER=EN ... &RCN=34907
'Bilingualism is now largely seen as being beneficial to children but there remains a view that it can be confusing, and so potentially detrimental to them,' says lead study author Dr Fraser Lauchlan from the University of Strathclyde. 'Our study has found that it can have demonstrable benefits, not only in language but in arithmetic, problem solving and enabling children to think creatively.'
Although an existing body of previous research supports the idea that to gain from the advantages of bilingualism a speaker must be equally proficient in both languages, few studies consider the cognitive benefits of bilingualism where one of the second languages is a so-called 'minority' language, such as Catalan, Basque, Scottish Gaelic or Sardinian. Most studies focus on speakers who are proficient in two well-recognised international languages such as French, English, Spanish, Italian, Russian or Portuguese.