(NaturalNews) Crows may understand cause and effect better than human six-year-olds, according to a study conducted by researchers from the University of California-Santa Barbara and the University of Auckland, New Zealand, and published in the journal PLOS ONE on July 21.
"We showed that crows can discriminate between different volumes of water and that they can pass a modified test that so far only 7- to 10-year-old children have been able to complete successfully," lead researcher Corina Logan said.
"The sky's the limit"
The research was conducted on the wild New Caledonian crows captured in New Zealand and transported to aviaries run at the University of Auckland. The birds were released after three to five months.
The researchers' first direct experience with the birds' intelligence came almost immediately, when they confronted the task of getting one bird into the testing room at a time.
"So I thought, let's pretend the sky's the limit and I can train them to do whatever I want," Logan said. "I started by pointing at the one I wanted and continuing to point until he or she flew out. I got to the point where I could stand outside the aviary and point at the one I wanted and it would fly out while the other birds stayed put."
Two of the birds even learned to recognize the names that the researchers had given them (007 and Kitty) and would fly into the testing room if the researchers called out their names.
The researchers performed two separate cognitive tests on the birds, both of which had been tried in previous studies. In the first test, the birds were offered two water-filled beakers that were the same height but had different widths. The beakers also contained a food treat that was too far down for the crows to reach.
"The question is, can they distinguish between water volumes?" Logan said. "Do they understand that dropping a stone into a narrow tube will raise the water level more?"
In a prior study, crows had been offered 12 stones, enough to fill up either beaker, and had not shown a preference. In the new study, the crows were given only four stones, and clearly preferred the narrower beaker.
"When we gave them only four objects, they could succeed only in one tube -- the narrower one, because the water level would never get high enough in the wider tube; they were dropping all or most of the objects into the functional tube and getting the food reward," Logan explained. "It wasn't just that they preferred this tube, they appeared to know it was more functional."
The second test involved two tubes wide enough to drop a stone into and two tubes that were too narrow. One of the wide tubes had a hidden connection to one of the narrow tubes, so that a stone dropped in the wide tube would cause the water to rise in the connected tube. The other wide tube had no connection.
A Cambridge University study previously found that while children aged 7 to 10 were able to figure out which tube to drop stones into to get a reward, younger children could not. A previous study also found that crows were incapable of the task.
In the new study, the researchers moved that two sets of tubes farther apart to better distinguish them. With this modification, the crow named Kitty was able to solve the task.
"We don't know how she passed it or what she understands about the task," Logan said.
"What we do know is that one crow behaved like the older children."