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If you’re thinking of trying to cheat a raven, you should know that these birds remember who treats them unfairly.

An experiment showed that ravens who had been taught to trade good food (bread) for even better food (cheese) were able to recall which individuals double crossed them. These trained birds were given an opportunity to trade bread for cheese with a stranger. In one situation, they faced a person who accepted the bread but then ate the cheese rather than surrender it. In another trial with a different person, the ravens received the cheese as expected. Some birds interacted with the "unfair" partner first but others dealt with the "fair" partner first.

Birds’ memories of these encounters were tested two days later and also one month later. In the test, they were offered a piece of bread and had the opportunity to choose to exchange it with the fair exchange partner, the unfair exchange partner or with a novel stranger. Two days after these experiences, six of seven birds chose to exchange with the fair partner and one bird chose to exchange with the novel person. Since the novel person acted in a neutral way by giving the bread back, that bird had a second opportunity to make an exchange and did so with the fair experimenter.