Ravens are clever creatures that seem to have a strong sense of justice. A new study, published by researchers from the University of Vienna and Lund University, reveals that they remember humans who offend them.

According to the study, which involved reciprocal interactions with nine captive-bred Corvus corax, ravens are able to recall when the human they interacted with cheated them out of getting a treat — even if it only occurred once.

Testing The Raven's Memory

The researchers began their trials by teaching the nine tame ravens to offer bread to a human experimenter. The human experimenter who receives the bread could either be fair by offering a piece of cheese to the bird in exchange for the bread or be unfair by accepting the piece of bread but eat the cheese themselves.

The birds were given a new set of tests two days later. The bread and cheese experiment was also performed but with an additional human experimenter whose reaction to the bread would be a mystery. Since the memory of getting tricked is still fresh in their minds, seven of the birds remembered who among the experimenters gave them a fair reward and chose accordingly.

The same test was conducted two months later and the research team was surprised to discover that the ravens still seemed to suspect and exhibit aversion toward the human experimenter who "cheated." The results were similar, with only two out of nine birds not outrightly choosing the fair experimenter.

The birds who did not exhibit recall were held back as observers prior to being allowed a chance to choose an experimenter. This means the first-hand experience is important in order for the trickery to be remembered.

According to the research team, such a result demonstrates that ravens have the capacity to remember a single positive or negative interaction for at least a month.

The Next Step For Raven Study

The study is a small and controlled experiment, but Matthias Loretto, a researcher from the University of Vienna who is not involved in the study, still believes that the results would make sense even in a bigger setting.

"I observe ravens so often in the field that it makes absolute sense that they would remember," Loretto said.

The experiments were done in order to observe the corvids' behavior and memory when interacting with humans. Researchers believe that the next step is to observe a raven's interaction with its own kind.