If someone lives actively in the two cultures of their bilingual repertoire, they gain the added possibility of hosting divergent (not really independent) personalities. This doesn’t really come as much of a surprise to me though. I wrote a paper years ago showing dramatic personality shifts from relationship to relationship, interaction to interaction, proposing a model that would define individual names to each relationship a person had, a hybrid being comprised of both parties’ traits, needs and expectations.

If someone acts and feels and responds differently when they are in different situations, does that make them a different person? Is their interaction with you any less or more valid? At what threshold of difference would we declare them to be a fully different person ready for psychiatric help?

the link: How switching language can change your personality - being-human - 25 June 2008 - New Scientist