Fountain points to work by Range et al. showing that dogs, like monkeys and chips, have a sense of equity and fairness. A dog may stop obeying a command if it sees that another dog is getting a better deal. Thus, species other than primates show at least a primitive version of inequity aversion, perhaps a precursor of a more sophisticated sensitivity to efforts and payoffs of joint interactions.
I wonder if this behavior also might possibly be related to the extensive breeding selection carried out on dogs over the past several thousand years which has made them, unlike monkeys and apes, very attentive to human moods and intentions.
(Note: I usually compose these blog postings several days in advance of their actual appearance, to keep free of deadline pressure. The downside of this is that I frequently see something I want to mention appearing immediately on, for example, the Op-Ed page of the New York Times. This bit on fairness in dogs is referenced by Gail Collins as relevant to the current U.S. automakers bailout controversy.)