That is so true -- one of my MAT profs always said "there is nothing new under the sun." That being said, the idea of "growth mindset" may not be new, but culturally, I do think it is a relatively recent shift. I worked with a really "old-school" teacher once who was always saying things like "they're a low class" or "he's a low student in math" or "she's high in reading" -- sometimes even making statements like these to the kids! She really believed that students either were naturally "good" at something or they weren't, and whether she meant it that way or not, her students took her words literally and would shut down in the areas she considered them to be "low" in. I have heard similar things since, and have seen the same on this board. So for you this might not be new, but for some and perhaps many, the idea is new. The brain research behind it -- the scientific evidence to back up these claims -- is relatively new, as well. So I suppose we could apply our growth mindset regarding other teachers (and ourselves) and their beliefs, as well.