A new study published in the journal Science finds honeybees are able to understand the concept of zero numerosity, joining the ranks of dolphins, parrots, and primates. Sci-News.com reports: The study authors set out to test the honeybee on its understanding, marking individual honeybees for easy identification and luring them to a specially-designed testing apparatus. The bees were trained to choose an image with the lowest number of elements in order to receive a reward of sugar solution. For example, the bees learned to choose three elements when presented with three vs. four; or two elements when presented with two vs. three. When the scientists periodically tested the bees with an image that contained no elements versus an image that had one or more, the bees understood that the set of zero was the lower number -- despite never having been exposed to an "empty set."