Atoms don't know they're being watched and using language like watched misleads people into thinking they do. Same issue as the double slit experiment. Watching is not passive, the correct term should be measured and the methods of measuring things affects them because you have to bounce particles off of things to measure them and thus measuring them (watching) changes their behavior.
Is it possible to measure with multiple devices that cancel each other out and get back to the same behavior as the unobserved system?
They actually are coming up with crazy ways to indirectly obtain measurement without interference or at least less, but this is about the limits of my knowledge on the subject.
Basically, this is called the observer effect. The process of observing something can change the thing you are observing.