Seriously though, the idea that mice might have a placebo effect is fascinating. I would have thought that the placebo effect would require some high-level form of self-awareness (which perhaps mice do have, I don't really know) and an understanding of at least the purpose of medicine. Maybe not though...
Edited to add: On a more serious note, I don't know if mice are susceptible to a Hawthorne-like effect http://psychology.about.com/od/hindex/g/def_hawthorn.htm Even physical science researchers have to deal with observer effects http://en.wikipedia.org/wiki/Observer_effect_%28physics%29
Edited to clean up brain-drained errors.
In brief, any time you have a subjective measurement (for instance, the experimenter assigns a number from 1 to 5 based on how "distressed" the mice -- or human patients -- look), that subjective measurement can be subtly biased. So if the experimenter doesn't blind his experiments properly, you can see a placebo effect in animal studies.
It is appropriate to refer to these studies as double or triple blind because the single blind usually refers to the patient.
Single blind: patients do not know which group they are in
Double blind: experimenters do not know the group identities
Triple blind: overseeing committees do not know the group identities
- http://www.socialresearchmethods.net/kb/relandval.php
- http://www.mathcs.duq.edu/~packer/Courses/Psy624/Validity.ht...
But basically, the placebo effect only exists for subjective measurements. (http://en.wikipedia.org/wiki/Placebo#Mechanism_of_the_effect) If something exists only in subjective measurements and not objective measurements... I'll let you draw your own inference.
Would that be a study where the mice are not aware of if they are in the control or not?
Has the placebo effect been seen in mice?