Eurasian jays shun reward for tastier delayed treat, study finds
The old saying states a bird in the hand is worth two in the bush but it appears Eurasian jays may beg to differ: researchers have found the corvids shun an immediate reward for a tastier, but delayed, treat.
What’s more, the team found the birds that showed the most self-control scored higher on a variety of cognitive tests, suggesting they were more intelligent.
Dr Alex Schnell, first author of the study from the University of Cambridge, said the relationship has previously been seen in chimpanzees and cuttlefish – species that diverged long ago.
“For the first time we show a link between self-control and intelligence in birds,” said Schnell. “Our research provides further evidence that self-control plays a key ingredient in what it means to be intelligent.”
Writing in the journal Philosophical Transactions of the Royal Society B, Schnell and colleagues report how 10 Eurasian jays were presented with a series of drawers with a different symbol on the front. Each contained a treat that was visible to the bird.
Over a series of trials the birds were taught the symbols related to how available the treat in the drawer was – while one drawer offered an immediately available treat, another drawer’s contents were only available after a delay, and those in a third drawer remained unavailable. The birds were also taught that once they chose a treat, the other options were removed.
After determining each bird’s treat preferences, the team explored whether, and for how long, the birds were prepared to wait for a worm from the “delay” drawer when a less-preferred snack, either bread or cheese, was immediately available.
The experiments are similar to the so-called “marshmallow test” – a famous challenge presented to young children by researchers at Stanford University in the 1960s and 70s, in which children were given the option of a single marshmallow immediately or two of the sweet treats if they resisted the urge to eat the first for a given period.
The results of the new study reveal that while the birds varied in how long they were prepared to wait, all of them delayed eating the immediate snack in the hope of something better. However the birds appeared to find waiting more difficult as the delay increased.
“Some only waited a maximum of 20 seconds and failed all the other trials with longer delays. By contrast, others waited up to five and a half minutes,” said Schnell.
The team adds that the birds showed little sign of waiting when the tastier treat was presented in the “unavailable” drawer, suggesting they only delayed gratification when it seemed worth it.
While other birds, including pigeons, have previously passed versions of the marshmallow test the latest study goes further, revealing that the jays that were able to wait for longer showed better general intelligence, as determined by five different cognitive tests.
Schnell noted studies in humans have previously suggested a link between self-control and general intelligence. However recent research has called into question the strength of findings suggesting that children who are more patient in the marshmallow test have better outcomes in later life, with the association greatly weakened once factors such as family background, early cognitive ability and home environment are taken into account.
Dr Manon Schweinfurth, an expert in animal behaviour from the University of St Andrews who was not involved in the work, welcomed the new study, noting the findings suggest selfcontrol and cognition is linked in the birds.
“This suggests that self-control and cognition is linked. Indeed, the same link has been found in children, too,” she said.
Schweinfurth added that given birds are only very distantly related to us and other primates the results suggest that either the link between selfcontrol and cognition is more universal or that it has evolved several times.
“Future studies are needed to understand the evolutionary origins of this link and whether the link between self-control and cognition is limited to spatial cognition or could be extended to other cognitive skills, such as social skills,” she said.