Research on crows shows that intelligence is related to more than absolute brain size

Researchers have found that absolute brain size is not the only factor determining intelligence. Corvid birds such as crows, magpies, and jays have brains that perform as well as chimpanzees on some tasks measuring intelligence.

The study shows that other factors than size such as neuronal density and structure play important roles in determining the level of intelligence. The study was led by researchers at Lund University in Sweden. Can Kabadayi, doctoral student in Cognitive Science said: "Absolute brain size is not the whole story. We found that corvid birds performed as well as great apes, despite having much smaller brains."

While intelligence is difficult to measure one aspect of it is inhibitory control. This is the ability of the brain to override impulses and choose a more rational mode of action. Researchers at Duke University in the United States carried out a large-scale study in 2014 comparing inhibitory control in 36 different animal species mostly primates and apes. The test involves a transparent tube with food placed inside and openings on both sides or ends. The challenge is for the animal to find the side openings rather than try to reach for the food directly. The study concluded that the great apes did best and that absolute brain size determined intelligence. The researchers did not try the test on birds.

The Swedish researchers along with others tried the test using corvid birds, ravens, as shown on the appended video but also New Caledonian crows, and jackdaws. Researchers from the University of Oxford and the Max Planck Institute of Ornithology also took part in the research:The team first trained the birds to obtain a treat in an opaque tube with a hole at each end. Then they repeated the test with a transparent tube. The animal impulse would naturally be to go straight for the tube as they saw the food. However, all of the ravens chose to enter the tube from the ends in every try. The performance of the jackdaws and the crows came very close to 100%, comparable to a performance by bonobos and gorillas.

Kadadayi said the test shows that bird brains are quite efficient in spite of their small size in absolute terms indicating, in contrast to the Duke study, that absolute size was not the only important factor in intelligence. Contrary to the idiom "bird brain" connoting stupidity silliness or lack of intelligence at least some bird brains are efficient and intelligent.

Other studies have shown signs of considerable intelligence in members of the corvid species. Of crows for example the Wikipedia entry says:

Recent research has found some crow species capable of not only tool use, but also tool construction. Crows are now considered to be among the world's most intelligent animals with an encephalization quotient equal to that of many non-human primates.The magpie also a member of the Corvus species is the only non-mammal able to recognize itself in a mirror. While absolute brain size may not determine intelligence relative brain size may be more important: The brain-to-body weight ratios of corvid brains are among the largest in birds, equal to that of most great apes and cetaceans, and only slightly lower than a human.

Some think the intelligence of corvids may be boosted by the relatively long period the young stay with their parents. Others note that young corvids are known to play many games and this may boost intelligence:Young corvids have been known to play and take part in elaborate social games. Documented group games follow a "king of the mountain"- and "follow the leader"-type pattern. Other play involves the manipulation, passing, and balancing of sticks. Corvids also take part in other activities, such as sliding down smooth surfaces. These games are understood to play a large role in the adaptive and survival ability of the birds.It seems intelligence is for the birds.