Parrots can use logic

Six African grey parrots from 10 to 35 years of age were shown containers, some empty and some containing food. The researcher shook one or both containers and then let the parrot choose between the two. The container with food rattled when shaken, and the parrot consistently chose that container. As a reward after choosing correctly, the parrot received a piece of walnut, a treat parrots like but rarely get. When the empty container was shaken (making no sound), the parrots chose the other container, inferring logically that the food must be there.

To find out whether this reasoning, and not avoidance of the non-rattling container, was what made the parrots choose correctly, another experiment was set up. A small loudspeaker was attached to both of the researcher’s wrists and hidden under her sleeves. The speakers were connected to an MP3 player that could play the sound of a walnut in a container. In some trials, the researcher shook a container and the wrist-speaker on the same side produced the rattling sound. In other trials, the sound came from the speaker on the opposite side. The parrots always chose the container that made the most noise, but only when the sound came from the correct side: when, for example, the container on the left was shaken and the sound also came from the left. The birds were, in fact, following the sound.

In the journal Proceedings of the Royal Society B, the researchers wrote that the parrots seemed to be able to reason that the food was causing the sound. The authors also assert that, in the earlier experiment, parrots were reasoning that, when an empty container was shaken, the food must be in the container that was not shaken. Until now, this kind of behaviour had been seen only in apes. Even very young humans don’t exhibit this behaviour. Two-year-old children cannot yet reason by hearing a sound that there is something in a box; this skill isn’t developed until three or four years of age.