Sheep Exposed To Heat Load Within Intensive Sheep Industries Book

I watched a documentary about koko the gorilla last year that seemed to show very convincingly that koko could communicate in sign language. i read a more sceptical discussion of the ability of great apes to learn language somewhere recently, though (i forget where, unfortunately), and somebody recommended this book. it's a review of all the ape language studies (before the 1990s, when the book was written, at least) and is very critical of the experimental design and analysis. it also reviews some of the literature on language development in children, in order to compare the two fields. the author does not believe that non-human apes have the capacity for language and does a thorough job of rebutting the claims to the contrary by showing that the use of signs or symbols can be explained as conditioned responses, rather than meaningful communication. it took me a while to start reading, because it is rather technical, but i found it very interesting.