By Dr. Becker
African grey parrots can find food rewards based not only on clues about where the food is, but also by making inferences based on an absence of clues.
The human ability to make logical inferences – in other words, to reason – is thought to be one of the foundations of intelligence. Scientists have tested many other species to see if they are capable of using reason, but to date, only apes seem to possess the skill.
African Greys Shine at the "Shaking Task"
In a study of African greys conducted at the University of Vienna in Austria1, researchers shook boxes containing walnuts and empty boxes so the parrots could hear the sound the nuts made bouncing around in the boxes.
The researchers varied the challenges by shaking both boxes or neither, just the empty box, or just the full one. The birds had to figure out not only that the noisy boxes contained food, but also that the lack of sound from one box meant the other box likely contained food. They had to pick the box with the walnuts to receive a treat.
The parrots were able to determine that a noisy box was a full box. But what really impressed the researchers was when presented with a box that made no sound when shaken, the birds consistently picked the other box. They seemed able to reason that it would contain food.
The study authors wrote: "Here, we report the first successful and instantaneous solution of the shaking task through logical inference by a non-ape species, the African grey parrot."
This is a test human children can't complete successfully until about the age of three.
Parrot Reasoning Ability is Influenced by Low Level Interferences
In order to insure the birds weren't just avoiding the silent box rather than reasoning the food was in the noisy box, researchers varied their shaking styles and combinations of shaking and sound.
The study authors discovered that when they shook the boxes horizontally, the birds picked the right ones, but not when they were shaken vertically. This led them to conclude grey parrots possess reasoning skills, but their ability to use those skills depends on the absence of low-level interferences.
According to study scientist Christian Schloegl of the University of Vienna, "The most important point is that higher intelligence is nothing that evolved only once. Comparable cognitive skills evolved several times in parallel in only distantly related species such as primates and birds."