Our brain doesn't reject foreign languages, the foreign languages doesn't sound sensible to our brains so the tries to manipulate every bit of information it knows. For instance, if you try to learn another language belonging to another culture, ancestry and origin you would need to try your best to conceive and perceive the language and use the mental capabilities that are inside you. No one in the world is "stupid", in my opinion everyone has an innate and genetic mental and logical ability. You have to exploit your ability by learning these languages and improve your IQ and EI as well. To learn languages for free visit http:/www.busuu.com/
the brain is used to processing information in a certain way that it learned and was wired by u from you years of using a single language. when you introduce another your still thinking in the first language making it much more difficult to learn another, its like trying to run an exe with a mac computer, its just hard to do and you need something to help usually.