There's a famous experiment on addiction involving rats and cocaine…..
The rats are put into a box with a button that administers a dose of cocaine. The rats become addicted and continue pressing the button for further doses of go-dust. A scientist was observing the experiment one day and remarked to his colleagues ‘ surely the stress of us watching, the plastic enclosure, etc. is contributing to the rats addiction and overall state of mind?’ So the scientists agreed this could be causing problems and decided to run a further test. Rather than the sterile environment, they would provide a more rat friendly one. It would be furnished with ratty things, stuff from nature: plants, branches, grass, etc. It would also include the aforementioned cocaine administration button so the scientists could continue their experiments and further investigate addictive behavior correlating to environmental stresses. Finally rather than the scientists standing around and watching, they’d install a camera. The experiment was set up and the scientists let it run for a couple of days with a mind to reviewing the footage later and discussing the hypothesis. Later they returned and reviewed the footage and just as they suspected the rats set up a clearing, installed DJ turntables and played psytrance over the 2 days they were away.