5 ideas
Borrowing from Jakob von Uexküll, de Waal argues that every organism lives in its own sensory and meaningful world, shaped by what its senses detect and what matters to its survival. Testing an animal outside its umwelt, such as asking a bat to use vision or a dog to ignore smell, measures the mismatch between the test and the animal rather than the animal's intelligence.
Earlier mirror tests on elephants had used small mirrors placed out of reach, and the elephants did not show self-recognition. When Joshua Plotnik's team installed a large, eight-foot mirror the elephants could touch and explore, an Asian elephant named Happy repeatedly touched a mark on her head that she could see only in the mirror.
When an animal fails a cognitive test, researchers too often conclude that it lacks the capacity instead of asking whether the test was motivating, species-appropriate, or fairly administered. Negative results are asymmetrically weak: one well-designed success shows a capacity exists, while a failure may only show a flawed experiment. Scientists should therefore be slow to deny cognition on the basis of null findings.
De Waal coins 'anthropodenial' for the reflexive rejection of humanlike characteristics in animals, and he treats it as at least as damaging as anthropomorphism. Because humans and other species share evolutionary ancestry, parsimony often favors assuming similar mechanisms behind similar behavior rather than inventing separate explanations for each species. The burden of proof should not fall automatically on those who claim continuity.
Rather than ranking species on one scale of intelligence with humans at the top, evolutionary cognition asks which mental capacities each species evolved to meet its ecological needs. Clark's nutcrackers, which store more than twenty thousand nuts in hundreds of locations and retrieve them months later, show a specialized memory suited to their way of life. Cognition is then compared across species through homology and convergence, as a branching bush rather than a linear ladder.