Is There a Diminishing Return?

I wish it was a study on this. I do too, because I think it's really exciting. And again, one of my great lemons is that I was too lazy to learn how to speak another language. So the next logical question would be, is there a diminishing return? If you know three languages, four languages, at some point do you stop having these good personalities or does it keep going on? Does someone know six languages, very different languages, are they switching between partial personalities inside of their head when these six languages?