Yes, I believe that's exactly what's happening. Investors as a whole are able to shape their own reality: If enough of them talk about valuations taking a south

Yes, I believe that's exactly what's happening. Investors as a whole are able to shape their own reality: If enough of them talk about valuations taking a southward turn or a "bubble popping," then it can quickly become a self-fulfilling prophecy. The opposite case is also true, of course.