Context:

Clay mentions reading this book about 15 years ago. He explains it was 'written by a neurologist and a horse trainer' and discusses the book's premise that horses don't have the brain capacity to 'like' or 'dislike' humans the way people anthropomorphize them. He uses this to justify his desire to keep a rattlesnake, arguing that the snake would be content in captivity. The book apparently examines horse behavior from a neurological perspective.