Corvids have the largest brains, relative to body size, in the avian world. In fact, relative to body size, corvids have the same sized brains as chimpanzees. It is suggested that they can even outperform this closest extant relative in cognitive tasks. These remarkable abilities have, for decades, inspired the curiosities of researchers, and a new study is expanding what we know about the intelligence of these ‘feathered apes’.
Edward Wasserman from the University of Iowa, USA, led an international team of scientists in testing cognition in hooded crows (Corvus cornix), and found that the crows were capable of ‘analogical reasoning’ – an ability previously thought to be limited to primates like humans and chimpanzees. Their surprising findings, recently published in Current Biology, showed that crows are capable of spontaneously solving matching tasks that involve relating different shape combinations to one another based on their colour.
The first part of the study involved caged hooded crows performing a task called ‘identity matching-to-sample tests’ (IMTS). This involved three cards and two cups placed on a plastic tray. Under one of the cups was tasty mealworms, and on each cup was a card with a coloured shape on each. A third card placed in the middle in front of the crow was an indicator card, and matched the card over the mealworm filled cup.
The hooded crows excelled and proved themselves extremely capable at creative problem solving, figuring out how to reap their rewards from the matched cards. So the test got a bit harder, the same crows entered into a second task called ‘Relational Matching-to-Sample tests’ (RMTS). This part of the experimental research was similar to the IMTS tests, in that they were performed with two cups and two cards, only this time the crows were tested with relational matching pairs. For example, a indicator card would have two same sized squares, but one red and one blue. For the cards over the cups, the empty cup played host to a card with a triangle and a square (one red and one blue) and the rewarding cup’s card had two same sized circles (one red, one blue). In over three quarters of the tests the crows responded correctly despite never having been trained to relate the shapes, showing they could relate the two cards even though they didn’t match exactly.
Wasserman was surprised by the crows advanced cognition and ability to show what he calls analogical reasoning and behavioural adaptation, “Most successful cases of relational matching-to-sample in animals, even primates, have come from extensive training involving supervised training: giving reward after correct responses and withholding reward after incorrect responses. The crows spontaneously solved the relational matching-to-sample task after only being trained on identity matching-to-sample, a feat previously achieved only by apes”. Wasserman also anticipates further research and more surprising findings. “Processing analogies has been said to be unique to humans. Now, we know that it is not. Many more revelations await the scientific study of cognition in animals,” he concluded.
Why exactly corvids have evolved such sophisticated cognitive abilities has been under scrutiny by researchers for years. One theory is that one of the main evolutionary drivers behind corvid cognition and intelligence is the fact that most corvids live in complex and dynamic social societies – a theory known as the social brain hypothesis. But Wasserman has his doubts. “Many believe that living in social groups is a part of the story, but I’m not yet convinced that sociality is the key factor”. It appears that more research is yet to be done, and this is just one study in a growing body of intriguing research into the fascinating abilities of these clever corvids.