Eurasian jays can be fooled by some common magic tricks but are less likely than humans to be deceived by other tricks, suggest the results from a series of experiments designed to explore how blind spots in attention and perception differ between humans and other animals.

The researchers showed birds and people three different sleight-of-hand techniques and found that the birds were misled by an illusion that depended on fast movements but fared better when faced with an illusion that relied on the viewer's expectations of how a hand would move. The team reported the findings Monday in Proceedings of the National Academy of Sciences.

"A magic trick works because it violates your expectations," said Elias Garcia-Pelegrin, a Ph.D. student in comparative cognition and evolutionary psychology at the University of Cambridge and first author of the study. "As such, it is quite interesting to use these magic effects to check if the expectations of other minds are like ours."

Probing how similarly attention and perception work in other animals compared with humans can give scientists insights into how these cognitive processes evolved, he says. Eurasian jays are a particularly appealing species for exploring these questions. They're members of the corvidae family, which also includes crows, ravens and magpies. These birds are experts at thwarting their thieving peers by using bluffing movements and manipulating food within their beak or concealing it in their throat pouch, the researchers noted in the study.

"In order to protect those caches ... they display a lot of methodologies that are quite similar to magic techniques," Garcia-Pelegrin said. "They use a lot of misdirection techniques [and] manipulation of the other bird's attention in order to ensure that the other bird doesn't know where they've hidden their food."

He and his colleagues trained six Eurasian jays to peck at the thumb of a fist holding a worm. The researchers next taught the birds to determine which hand contained the treat after a person presented the worm in one hand, overtly transferred it to the other hand, and then closed both fists to conceal it. 

The team then tested how susceptible the birds were to three different sleight-of-hand techniques. The first two experiments featured a palm transfer and a French drop, during which, respectively, the performer conceals the object within or allows it to fall into the palm of one hand while pretending to move it to the other hand. The third technique, known as a fast pass, involves passing the object from one hand to the other so quickly that the spectator doesn't notice the transfer.

For the sake of comparison, the researchers also performed versions of each trick that were executed in a slow or potentially less deceptive manner or involved transferring or retaining the worm instead of faking these actions. 

The researchers showed videos of Garcia-Pelegrin performing these tricks with worms to 80 people between the ages of 16 and 60 and showed recordings of more "typical" versions of the tricks, involving coins, to an additional set of 165 participants. The researchers noticed similar reactions from both groups of people: Humans were more likely to choose incorrectly when they observed the "genuine" trick and to choose correctly when they observed the modified versions.

Unlike people, Eurasian jays were not taken in by the palm transfer or the French drop. These effects depend upon the spectator anticipating, incorrectly, that the object will be passed between hands. The birds, however, were not encumbered by the same expectations.

"If they did not physically observe the reward moving from one hand to another, they would just choose the initial hand," Garcia-Pelegrin said. "Possibly, the concept of grabbing is such an alien concept that it makes no sense to a bird."

The jays were misled by the fast-pass effect, though, suggesting that they fail to perceive fast-paced movements. Further experiments will be needed to understand whether the explanation lies in a difference in how bird vision works compared with that of primates, or whether the birds aren't paying attention properly. Garcia-Pelegrin is also interested in investigating whether jays that stash their food more swiftly can take advantage of these "blind spots" and are less likely than slower birds to have food pilfered, and in determining to what extent this vulnerability extends to other species. 

The experiments will also need to be repeated with a greater number of avian participants and with more magicians to verify that the reactions Garcia-Pelegrin and his team observed in their small group of jays are representative. 

Ultimately, Garcia-Pelegrin hopes to design magic effects that are tailored to the cognitive abilities of birds rather than people.

"I wish I was creative enough at this stage to create a magic effect that truly encapsulated the Umwelt — the essence — of the bird in order to see whether I would be able to capitalize on their own expectations," he said. 

The study, "Exploring the perceptual inabilities of Eurasian jays (Garrulus glandarius) using magic effects," published May 31 in PNAS, was authored by Elias Garcia-Pelegrin, Alexandra K. Schnell, Clive Wilkins and Nicola S. Clayton, University of Cambridge.