than curiosity. In 2005, experiments were conducted on the ability of capuchins to use money. After several months of training, the monkeys began exhibiting behaviors considered to reflect an understanding of the concept of a medium of exchange that were previously believed to be restricted to humans (such as responding rationally to price shocks). They showed the same propensity to avoid perceived losses demonstrated by human subjects and investors. During the mosquito season, they crush millipedes and rub the result on their backs. This acts as a natural insect repellent. Self-awareness When presented with a reflection, capuchin monkeys react in a way that indicates an intermediate state between seeing the mirror as another individual and recognizing the image as self. Most animals react to seeing their reflections as if encountering another individual they do not recognize. An experiment with capuchins shows that they react to a reflection as a strange phenomenon, but not as if seeing a strange capuchin. In the experiment, capuchins were presented with three different scenarios: Seeing an unfamiliar, same-sex monkey on the other side of a clear barrier Seeing a familiar, same-sex monkey on the other side of a clear barrier A mirror showing a reflection of the monkey In scenario 1, females appeared anxious and avoided eye-contact, while males made threatening gestures. In scenario 2, there was little reaction by either males or females. When presented with a reflection, females gazed into their own eyes and made friendly gestures, such as lip-smacking and swaying. Males made more eye contact than with strangers or familiar monkeys but reacted with signs of confusion or distress, such as squealing, curling up on the floor, or trying to escape from the test room. Theory of mind The question of whether capuchin monkeys have a theory of mind—whether they can understand what another creature may know or think—has been neither proven nor disproven conclusively. If confronted with a knower-guesser scenario, where one trainer can be observed to know the location of food and another trainer merely guesses the location of food, capuchin monkeys can learn to rely on the knower. This has, however, been repudiated as conclusive evidence for a theory of mind as the monkeys may have learned to discriminate knower and guess by other means. Until recently it was believed that non-human great apes did not possess a theory of mind either, although recent research indicates this may