I read Julian Jaynes' book many years ago and I was very impressed by it. I did not accept his central thesis, that bicamerality dominated human thought process until recent historical times, and somehow evolved into our current mode of unicameral thought.

However, I think he was on the track of something, his scholarship was astonishing and his book is filled with insights into human behavior which I have found very useful. I have come to many of the same conclusions you have re a recent change in perception and expression. But my evidence is from a different source. I am finding the communications of popular media, such as television and music, to be changing its methods, especially in advertising techniques. Media artists and commercial propagandists are our most skilled psychologists, they will be the first to identify and exploit changing human perceptions, it would be wise to follow their work closely.