We've all been there: You're planning to save dessert for after dinner, but on your way home from work you stop at 7-Eleven and binge on a box of stale donuts. A new study in Animal Behavior finds that birds might have more self-control than you in that situation.
German researchers discovered that ravens and crows have the ability to suppress their cravings—once they know that there's better food on the table.
Friederike Hillemann, a Master's student at Göttingen University, tested the decisiveness of corvids by experimenting with delayed gratification—turning down an immediate reward for a better reward later. First, she and her colleagues observed the dietary preferences of seven carrion crows and five common ravens. All 12 captive-bred birds were presented with choices of fried pork, beans, bread, sausage, corn, grapes, and cheese, with the researchers recording which entrées each bird preferred.
The team then experimented with two different systems: accumulation and exchange. During accumulation, the researchers made a pile of food in front of the bird. At each given interval they would add another piece, for a total of four pieces per pile. During exchange, the researchers gave the bird one scrap of food, and then swapped it out for a more desirable option. Each subject underwent a training phase before being tested in both accumulation and exchange. The majority of the birds were able to tolerate the exchange, but only a few could curb their impulses during accumulation. The most successful individual, a female, held out for over 10 minutes.
Hillemann's results confirmed findings from studies on other animals that revealed that waiting is hard, but not impossible. Impulse control has been previously noted in Goffin cockatoos, as well as orangutans and other primates.
But Hillemann's study uncovered two additional aspects of self-control. The birds didn't improve their performance over time; practice didn't make the birds wait longer. Also, age didn't play in a role in delaying gratification. The 17-year-old raven wasn't any better at waiting than the 1-year-old crow. Sex, on the other hand, may have been a variable, as there was a skew toward females delaying longer than males.
"Cognition studies such as this one reveal how animals process the world," says Hillemann. She chose to focus on corvids over other birds because of their complex social behaviors and cognitive abilities. Crows and ravens are known to hoard food and exhibit altruism as well.
Yet Hillemann says that sociality isn't the only driving force behind impulse control. Environmental factors, like competition and scarcity, can be crucial to the development of this ability. "From an ecological perspective, food-storing behavior offers an illustrative example of how the need to plan for the future may have reinforced the evolution of self-control," says Hillemann. Crows and ravens thrive in volatile, humanized areas, so it's no surprise that they've evolved to be decisive about foraging.
One of Hillemann's goals is to help spread the word that ravens and crows are complex and intelligent animals, rather than pests. True, they might try to steal your stale donuts. But ultimately, they're doing you a huge favor.