If I'm remembering correctly there is an age (younger) where we are more receptive to patterns in regards to LA, but we don't differentiate the language received. "All" input in this stage is valid input that kid brain associates meaning to, which slowly gets weeded out (lost) if you don't use it into adulthood. However, we are all generally speaking, on an even playing field developmentally as we age after that point in regards to learning a new language. Adults just tend to have less free time to devote to learning a new language as a young adult, etc.