Surely this is a prime candidate for the Hawthorne effect?
From Wikipedia: http://en.wikipedia.org/wiki/Hawthorne_effectThe Hawthorne effect is a form of reactivity whereby subjects improve or modify an aspect of their behavior being experimentally measured simply in response to the fact that they are being studied, not in response to any particular experimental manipulation.
From Wikipedia: http://en.wikipedia.org/wiki/Hawthorne_effect The Hawthorne effect is a form of reactivity whereby subjects improve or modify an aspect of their behavior being experimentally measured simply in response to the fact that they are being studied, not in response to any particular experimental manipulation.