New research is finding that reptiles are more emotionally complex than previously thought. In a recent study, U.K. scientists identified what they describe as “mood states”—emotional experiences that are more than momentary—in red-footed tortoises. They trained 15 tortoises to associate one location with food and another spot with no reward. Then they presented the tortoises with bowls placed between the two locations; the tortoises approached more quickly when the bowls were closer to the food spot, indicating optimism. Later they measured anxiety by presenting each tortoise with an unfamiliar object. The tortoises that were most optimistic in the earlier test showed the least anxiety, appearing to be buffered by their good moods. Scientists aren’t sure yet if the findings can be extrapolated to other reptiles, but they plan to do more tests. “This is an exciting finding that represents a significant shift in our understanding of what reptiles can experience,” says study author Oliver Burman, “with important implications for how we care for these animals in captivity and interact with them in the wild.”