Are Crows Mind Readers ... Or Just Stressed Out? - [Article]

"Soon... my Lego castle will be complete!
Your people intelligence is no match for my bird intelligence"

(ScienceNOW, 10, Jan 2013) - Are crows mind readers? Recent studies have suggested that the birds hide food because they think others will steal it — a complex intuition that has been seen in only a select few creatures. Some critics have suggested that the birds might simply be stressed out, but new research reveals that crows may be gifted after all.

Journal article: Corvid Re-Caching without ‘Theory of Mind’:A Model

Cracks first began forming in the crow mind-reading hypothesis last year. One member of a research team from the University of Groningen in the Netherlands spent 7 months in bird cognition expert Nicola Clayton’s University of Cambridge lab in the United Kingdom studying Western scrub jays, a member of the crow family that is often used for these studies. The Groningen team then developed a computer model in which “virtual jays” cached food under various conditions.

In PLOS ONE, they argued that the model showed the jays’ might be moving their food—or recaching it—not because they were reading the minds of their competitors, but simply because of the stress of having another bird present (especially a more dominant one) and of losing food to thieves. The result contradicted previous work by Clayton’s group suggesting that crows might have a humanlike awareness of other creatures’ mental states—a cognitive ability known as theory of mind that has been claimed in dogs, chimps, and even rats.

In the new study, Clayton and her Cambridge graduate student James Thom decided to test the stress hypothesis. First, they replicated earlier work on scrub jays by letting the birds hide peanuts in trays of ground corn cobs—either unobserved or with another bird watching—and later giving them a chance to rebury them. As in previous studies, the jays recached a much higher proportion of the peanuts if another bird could see them: nearly twice as much as in private, the team reports online today in PLOS ONE.

Then came the stress test. First, Thom and Clayton gave the jays trays with the ground cobs but no food to hide in them—a so-called “sham” session. Then, in a second session, they gave the birds new hiding trays and bowls of peanuts to hide. When the jays were done, the experimenters removed the trays and stole all of the peanuts. Finally, after a short break, the researchers gave each bird yet another round of food, a new tray to hide it in, and one of the trays it had seen earlier: either the sham tray or the ransacked “pilfer” tray. The jays had 10 minutes for recaching.

If the Groningen model was correct, Thom and Clayton argue, the stress of discovering that food was missing from the pilfer tray ought to drive jays to cache more peanuts than those presented with the sham tray. In fact, there was no difference, even though corvids have excellent memories for hidden food and remarkable abilities to find it again. The hypothesis that jays have theory of mind remains on the table, Thom says.

Thom and Clayton have “definitely shown that scrub recaching is not as simple as the [Groningen] model presents it,” says Elske van der Vaart, lead author of the Groningen team’s earlier report, who is now at the University of Amsterdam. But she argues that there is still room for doubt about what the results mean. For example, the sham condition—in which the jays had no food to cache—could have stressed the birds as much as the stolen peanuts in the pilfer condition did.

Amanda Seed, an animal cognition researcher at the University of St. Andrews in the United Kingdom, says the Groningen model’s failure to predict the birds’ caching behavior in the new experiments could “bring the model down like a pack of cards.” But researchers still have to rule out other possible explanations, she says. For example, the birds given pilfered tray may have noticed the missing peanuts too late to affect their overall caching rate, or they may have spent much of their time looking for the missing nuts instead of hiding the new ones. The Cambridge and Groningen groups are planning more work with both real and “virtual” birds to see what is really going on. “I applaud them for rising to the challenge,” Seed says.

Crows can 'reason' about causes, a recent study finds

Curious crow is curious

(BBC Nature, 18, Sept, 2012) - Tool-making crows have the ability to "reason", say scientists.

In an experiment, researchers found that crows were more likely to forage when they could attribute changes in their environment to a human presence.

This behaviour may suggest "complex cognition", according to a study published in the Proceedings of the National Academy of Sciences.  Until now the ability to make inferences based on causes has been attributed to humans but not animals.

The study was a collaboration between researchers from the University of Auckland, New Zealand, the University of Cambridge, UK and the University of Vienna, Austria.

In their experiment eight wild crows used tools to remove food from a box.  Inside the enclosure there was a stick and the crows were tested in two separate series of events that both involved the stick moving.

In one instance a human entered the hide and the stick moved. In the other, the stick still moved but no human entered.  On the occasions when no human was observed entering the hide, the crows abandoned their efforts to probe for food using a tool more frequently than they did when a human had been observed.

According to the scientists, the study proved that crows attributed the stick's movement to human presence.

The results indicated that neither age nor sex was a predictor of the behaviour with juveniles, males and females displaying the same behaviour.  Scientists said that the kind of "reasoned inference" shown by the New Caledonian crows under these controlled conditions could also be utilised in the wild to anticipate danger or food.

The study is the first to suggest that animals have the ability to make reasoned inferences, although scientists added that the phenomenon could be more common among animals than previously thought.

Journal reference: New Caledonian crows reason about hidden causal agents - http://www.pnas.org/content/early/2012/09/10/1208724109

Crows can remember and differentiate human faces

"I know I know you"
 - The Crow (1994)

(New Scientist, Sept, 10, 2012) - You can run from a crow that you've wronged, but you can't hide. Wild crows remember human faces in the same way that mammals do.

Crows can distinguish human faces and remember how different people treated them, says John Marzluff of the University of Washington in Seattle.

To work out how the crows process this information, Marzluff had members of his team wear a latex mask as they captured 12 wild American crows (Corvus brachyrhynchos). The crows learned to associate the captor's mask with this traumatic experience. While in captivity, the crows were fed and looked after by people wearing a different mask.

After four weeks, the researchers imaged the birds' brains while they were looking at either the captor or feeder mask. The brain patterns looked similar to those seen in mammals: the feeder sparked activity in areas involved in motivation and reward, whereas the captor stimulated regions associated with fear.

The result makes sense, says Kevin McGowan of Cornell Lab of Ornithology in Ithaca, New York. Crows don't mind if humans are in their habitat – but they need to keep a close eye on what we do.

Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1206109109