What research is there to show whether or not animals feel pain?

Question: What research is there to show whether or not animals feel pain?
- Keywords:
  animal testing,
  ethical
Asked by annadiamond to Laura on 12 Mar 2012.
- Laura Waters answered on 12 Mar 2012:
  
  Animals feel pain, no doubt about it. I just don’t see the point of testing on animals as we often react very differently to them so unless you wanted to know how a mouse behaved you shouldn’t test on a mouse!

Question: What research is there to show whether or not animals feel pain?