By Michael Balter
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.
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.
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