How Intelligent Are Vertebrates?

Abstract

One key publication in comparative intelligence research was the book “Brain and intelligence in vertebrates” by the British psychologist Euan MacPhail, which was published in 1982. Here, MacPhail proposed a thesis that shocked many of the experts in the field by stating that all vertebrates turn out to be equally intelligent, if their behavior is studied under “fair” conditions, i.e., under those who take into consideration their specific living conditions. At least—so the argument of the author goes—there are only quantitative, but no qualitative differences in cognitive abilities, i.e., those that are present in some, but completely absent in other groups. According to this view, birds and mammals are not generally more intelligent than teleosts, amphibians, or reptiles. The one exception is human beings, because only they have language and, consequently, consciousness.