The term "birdbrain" is falling out of fashion, and rightly so.
Scientists interested in animal intelligence overlooked birds in favor of humankind's closest relatives, the great apes, for many years. Due to our similarities and shared evolutionary history, the intelligence of apes is easier for us humans to recognize and test. But recent research is finally giving smart birds the recognition they deserve.
Avian intelligence has many forms. Jays plan ahead and anticipate future events when caching food, and use sophisticated tactics to protect their food caches from thieving neighbors. Crows are clever in their use of tools and in their ability to use imagination and insight when solving problems. Perhaps the birdbrains that have captured the public's interest most are the parrots, some of whom can actually tell us what they're thinking.
Irene Pepperberg's long and fruitful collaboration with an African grey parrot named Alex made celebrities of them both. Alex had a large vocabulary and was able to use it in a sophisticated way, differentiating between meaning and syntax. He also acquired impressive numerical abilities, including counting and understanding the concept of zero.
Now, a new study shows African grey parrots are capable of making logical inferences based on cues from their environment. Christian Schloegl and colleagues from the University of Vienna were able to demonstrate the parrots' impressive skills with an elegant test that had, until now, never been administered to birds.
In previous experiments, African grey parrots were given a simple task. The birds were shown a pair of closed canisters, one with food inside and the other empty. The researchers opened the empty canister, showed it to the birds, and resealed it. Afterward, when given the chance to choose one of the canisters, the parrots reliably chose the one with the food inside. The researchers interpreted this as evidence for the parrots' inferential reasoning ability; if there are two canisters and one is empty, then the other one must have the food. Critics, however, said this test was too simple to make that claim. After all, the animals could just be avoiding the empty canister, rather than making the leap to realizing its emptiness implied the presence of food in the other canister.
So Schloegl and his colleagues devised a more difficult task. In the new study, published August 8 in the Proceedings of the Royal Society B, the researchers again gave the parrots a choice between two canisters, one containing food and one empty. But instead of showing them what was inside, the researchers shook one of the canisters, so the parrots could hear either the sound of walnuts rattling around inside or silence.
The birds passed the test with flying colors. They consistently chose the food canister, whether it was shaken or the empty canister was shaken. This means they were able to figure out that a noisy shake indicated "food inside" and a noiseless shake indicated "no food inside, so food must be in the other one."
Schloegl and colleagues introduced one more variation to the task to address any concerns that the birds might be simply avoiding the silent canister. Instead of using the actual sounds made by the shaken canisters, the researchers wore small speakers on their wrists that played shaking noises. This allowed them to separate the shaking sound from the shaking action. Sometimes they shook the canister in one hand while playing shaking sounds from the opposite wrist. Other times, they played the sounds from the same side as the shaking action. The parrots only made the correct choice when shaking action and shaking sound came from the same side. They made inferences about what the canisters contained based on the connection between the visual and auditory cues, and not from either cue alone.
If you're still not wowed by the reasoning prowess of parrots, consider this: no other non-primate species has successfully completed this type of task, and humans do not usually develop this skill until they are about three years old. Both monkeys and dogs have been tested and failed. This study is the first report of a non-ape species solving this type of task through logical inference.
The parrots in this experiment also solved the puzzle instantaneously - they did not learn the correct choice through trial and error. That they were able to make these judgments based on the presence or absence of sounds associated with food confirms that they are capable of making abstract, logical inferences.
This study shows the ability to reason is not limited to humans, or even to primates. The sophisticated cognitive skills of African grey parrots provide evidence that this type of intelligence has evolved in parallel in distantly related animals, resulting in a very impressive birdbrain.