Mirror, Mirror on the wall, pray tell. Who am I?

Many years ago, in the Zoological Gardens, I placed a looking-glass on the floor before two young orangs, who, as far as it was known, had never before seen one. At first they gazed at their own images with the most steady surprise, and often changed their point of view. They then approached close and protruded their lips towards the image, as if to kiss it, in exactly the same manner as they had previously done towards each other, when first placed, a few days before, in the same room. They next made all sorts of grimaces, and put themselves in various attitudes before the mirror; they pressed and rubbed the surface; they placed their hands at different distances behind it; looked behind it; and finally seemed almost frightened, stared a little, became cross, and refused to look any longer.

C. Darwin, Expressions of the emotions in man and animal (p.g. 140)

On the island of Cayo Santiago, Puerto Rico, a large population of rhesus monkeys lives year round. During the year, animals are trapped for TB testing and for other biomedical purposes. To trap the animals, personnel sit in small huts, looking out at one way mirrors. Over the course of my studies since 1988, I have never seen an adult show interest in the mirrors. On a few rare occasions, I have seen infants jump up and take a brief look.

In the summer of 1997, one of the mirrors broke into several small pieces. Four females in one group picked up these pieces, and carried them around for several days, staring intensely at their reflection. There were absolutely no signs of aggression. The video clip presented here is a sample taken with a digital video camera.

Here's my impression. It seems that they are staring at their reflection and holding it close to their face so that they can pick up on eye gaze and the details of their face. Such behavior stands in striking contrast to other reports suggesting that rhesus, together with most other monkeys, respond aggressively to their mirror reflection. Why the difference? One possibility, that we will test, is that in contrast to other studies using large fixed mirrors, here we have a situation where the individual can carry around its mirror, and thus, its reflection. Perhaps the capacity to carry around the mirror facilitates their understanding --- they can't possibly carry around another individual. So, the logic might run like this: I am holding a mirror in my hand. There is another monkey's face. It can't be another monkey because I am not carrying one. It must be me.

Well, that is a speculation. Your speculations welcome.