The Clever Hans Problem and Research on Animal Cognition

As Denyse O'Leary will likely discuss in her new series "Animal Minds," a number of research studies claim to show that under some circumstances animals are capable of abstract thought. I believe that those conclusions are wrong, and that animals are not capable of abstraction.

Animals think particularly, not abstractly. That is, animals think about particulars (individual things) and about perceptions connected to the particulars, but they are not capable of abstracting universal concepts...