well the author has supplied plenty of references, to scientific, biological and ornithological journals up to 2015 for that chapter. I haven't followed them up yet, but chapter 1 is all about definitions, and it's all contested. Intelligence is very difficult to define (except for the stupid). But what I've read of the book so far fits with what I know about my birds and their behaviours.Hmmm, I was thinking about avian brains and the neuron paths and speed. There is also the problem of defining intelligence. No matter, it's the tribes in Catalonia who were as thick as bricks in that case even though they would have needed more learning time due to a much larger range of experiences. Im calling bullshit on this one, or poor science.