Since our brains are intaking information at a phenomenal rate during ages 4-8 (more than at any other time in our lives), any sounds we hear or say later will be matched up with those pre-existing ones. And since our first language doesn't have all possible sounds, we change L2 sounds (that don't have existing associations) into L1 sounds.
As Radical English teachers, we've known this for such a long time that it's strange to see it lauded as a "new discovery". It seems we have to wait for "science" to "research" it and "prove" what radical teachers already know, that language learners learn best when we teach patterns, not rules! http://bit.ly/1nlaOGk