Хоторнский эксперимент

Hawthorne Experiment.

Advantages:

During the experiment the performance of the group has increased (Not because of improving conditions, but because of the communication and collaboration) 

Disadvantages:

there were personnel changes, that is the workers hostile watching the situation changed for those who would like to work in such conditions (that is attended only those workers who are more willing, not all workers)

Conclusion: This experiment showed that workers are willing to actively work in such conditions, when they are paying attention to when they are being watched. That is, When a person sees that his actions followed, he tries to work better.

Source: http://psyfactor.org/lib/hotornskiy_experiment.htm