The results of the study aren't really surprising when one considers that inequity aversion in humans is most pronounced during relatively early childhood. How often do parents of two-year-olds hear something like, "Not fair! Suzie got more than me!" ? The fact that it is something human children learn so early and easily would seem to indicate that it is a trait passed down from our "pre-human" ancestors, not a "learned behavior".

I would be very interested to see the same type of study performed with dogs to see if inequity aversion is strictly a primate characteristic or if it is even more deeply ingrained in the mammalian psyche.

Bruce