When  mice are exposed to pain their face reflects it.  How many centuries has it taken to discover that?  Researchers in Canada report that “This is the first study that has examined facial expression of pain in non-human animals.”  They have made a “mouse grimacing scale.”  This reminds me of the use of aversive stimuli in shaping human behavior.  The scientists (as though it was news to them)  decided that  altering the mood of the subject  contaminated the results.  It sounded like the scientists were surprised that their subjects didn’t like being shocked.

(Mice: The Week May 28, 2010) (aversive conditioning : Azrin and Holz, 1966).