Is 'bird brain' really an insult?

Calling someone a bird brain is a poor insult, because the evidence points the other way. Birds have relatively large brains compared to their head size, and bird brains have two to four times the neuron packing density of mammal brains. Corvids, the crow family, and parrots are often considered the most intelligent birds, and among the most intelligent animals in general. The brain-to-body size ratio of parrots and crows is comparable to that of higher primates.

The old idea was different. At the beginning of the 20th century, scientists argued that birds had hyper-developed basal ganglia, with tiny mammal-like forebrain structures. Modern studies have refuted this view. In birds, a forebrain region called the pallium has a structure reminiscent of the mammalian cerebral cortex, and it has even been suggested to be an equivalent neural basis for consciousness.

Then there is Alex, a grey parrot who was the subject of a thirty-year experiment by animal psychologist Irene Pepperberg. In 1999 Pepperberg said he could identify 50 objects, recognise quantities up to six, tell seven colours and five shapes apart, and understand bigger, smaller, same and different. Every night when she left the laboratory he said, "You be good. I love you. See you tomorrow."

Yet scientists disagree about what that shows. Pepperberg did not claim Alex used language, only a two-way communications code. Herbert Terrace argued that Alex performed by rote, guided in every situation by an external stimulus.