As I'm even thinking now more and more in English, it surprises me that occasionally German words would unconsiously sneak in when I'm speaking English. A group of Dutch psychologists now found an explanation:
Bilinguals Are Unable To 'Turn Off' A Language Completely, Study Shows
ScienceDaily (2009-08-19) -- With a vast majority of the world speaking more than one language, it is no wonder that psychologists are interested in its effect on cognitive functioning. For instance, how does the human brain switch between languages? Are we able to seamlessly activate one language and disregard knowledge of other languages completely? ... > read full article