Hopefully not wandering too far off topic, but, Jondo, re: Baxter's experiments, there is a recently noticed problem with scientific research ... the 'decline effect' and 'replication crisis' (see Wiki articles on both). It seems that trials and experiments, when repeated, often no not produce the trusted results that the originals had, no one knows why. It is causing concern in the scientific community. I, personally, have a problem with 'scientists' who have already decided what is possible and what is impossible, before using the scientific process to explore a hypothesis (seems to drift into 'dogma' and undermines science's specialty!)
BTW, another great book on animal intelligence is 'Animal Wise' by Morrell... re: fish, see the chapter on the archer fish. Frans de Waal has long explored animal emotions... especially in primates. I, too, find this subject utterly engrossing!