Ravens have the same level of self-control as chimpanzees despite having tiny brains, a new study has found. This provides strong evidence that intelligence has little to do with brain size.
Researchers from Lund University in Sweden tested the motor self-regulation of ravens, jackdaws and New Caledonian crows, members of the exceptionally clever corvidae family of birds that also includes magpies, rooks and jays. The study, published in Royal Society Open Science, found that ravens exhibit very high levels of self-control, something that is a strong indicator of overall intelligence.
The birds's intelligence was assessed using what the study refers to as the 'cylinder task'. Researchers started by placing a treat into an opaque cylinder in full view of the bird. The cylinder had a hole at each end that provided access to the treat and the researchers made sure that the birds knew how to get to the cylinder's contents.
The opaque cylinder was then replaced with an otherwise identical transparent cylinder and more treats were inserted into this tube. The tests of the birds' self control was whether they would bash their beaks on the transparent cylinder while trying to get to the treats or remember how to get to the goods through the holes on either end. A 'fail' was recorded if a bird pecked at the tube to try and retrieve the food.
Researchers compared their results with studies of great apes performing the cylinder task and found that the birds performed just as well, despite having much smaller brains. Ravens were the cleverest of the birds and completed the task correctly 100 per cent of the time, exactly the same result as chimpanzees. The jackdaws and new caledonian crows scored 97 and 92 per cent, outperforming bonobos and gorillas, which scored just 95 and 94 per cent at the cylinder task.
"Our results show that [apes and corvids] share fundamental cognitive mechanisms," the study concluded. The results also suggest that absolute brain size has very little to do with the intelligence of an organism.
A raven's brain is 26 times smaller than that of a chimpanzee, yet both species recorded identical scores in the motor self-control test. The difference between jackdaws and bonobos is even more pronounced, as the birds have brains that are 70-94 times smaller than the equally-intelligent great apes.
However, the study did find that brain size across bird species did have an impact on their performance in the cylinder task. The best performers, ravens, have slightly bigger brains that either jackdaws or New Caledonian crows.
This isn't the first study to suggest that ravens are far from bird-brained. Researchers from the Universities of Houston and Vienna have found that ravens are capable of abstract thought and can imagine themselves being spied upon. The study tested their ability to hide food and found that the birds still stashed their treats if they thought they were being watched, even if there was no actual evidence of a competitor.