Birds of the corvid family such as crows, magpies and ravens have built quite a reputation for their smarts, with a history of hitching rides on bald eagles and remembering the faces of their captors. Researchers have further explored this trait in ravens by intentionally ripping the poor birds off in a trade, then returning at a later date to see whether they remember being hard done by.

The research was led by the University of Vienna and conducted by scientists from both Austria and Sweden. The team ran experiments with seven tamed ravens to find out more about whether these birds can interpret negative behaviors from various individuals, and if so how they respond.

The researchers trained the ravens to trade treats with a person, exchanging a piece of bread for a piece of cheese, which they much prefer to eat. But once the birds had become accustomed to this deal, some of the humans would occasionally dupe the bird, taking their bread for themselves and eating it along with the cheese.

Two days later, the birds that had been ripped off would not trade with those same people, but would do so with others that had traded fairly or not yet at all. Impressive memories right? Well the researchers returned two months later, and still only one of the birds was willing to trade with one of the deceivers. These results, the team says, show that ravens are able to remember individuals that are worth cooperating with, even after a single interaction, hinting at how they might behave during social interactions with other ravens.

The research was published in the journal Animal Behavior.