How can the effects of pain on cognitive functions be tested in an ethically accepted way? I have devised a study that may provide an ethical way to invoke similar behaviours in participants, as those demonstrated by individuals in pain. Obviously it is extremely hard to correctly test people's cognitive abilites in a lab when looking at the effects of pain. 

My question is, would anyone be able to mention some citations I could look into where they have attempted to recreate in a lab an ethical way to demonstrate the same responses that pain creates in order to test memory, and other cognitive processes?

My Idea is to utilize different diluted sample of capsaicin, and provide comparisons to the type of hot pepper for participants. I believe that if I could find a way to gain ethical approval that the feelings and then behaviors one experiences when eating an extremely hot pepper, are in fact similar to those of a person in the position of an aactual injury. If in fact correct it can provide a safe and controlled way to test cognitive functioning under these conditions. high fat dairy products would be on hand for the participants to assist, and in fact the distraction of participants for using on those to relieve symptoms during testing would add to the collective data. This can provide important information related to victim testimony, ability of individuals to make appropriate decisions, or give consent under pain.

I understand this is long, and that it is touchy within the ethics views, which is why I present to you my intent, thoughts, and ask for assistance in gathering other literature from those who have succeeded in attempting to study this in the lab as opposed to case studies.
Pain is a form of stress. I would replace pain with another, ethically less problematic stressor. If you would want to do it elegantly, test a group of subjects with chronic pain (anything; e.g., back pain) and use a control group where you submit a group of healthy subjects to a stress test (e.g. Stroop test - huge body of literature on this) and a third group without a stressor. See if the pain group matches the stressed group and whether they are both significantly different from the controls. If yes, you've found a way to prevent ethically kind of unacceptable tests, where the search for volunteers will likely be very difficult too.