Everyone has seen the experiments where monkeys and rats in cages will sip cocaine or heroine laced fluids rather than water until they die.

An experiment called Rat Park (check wiki) conducted many years ago by an addiction researcher surprised. Be mindful there is a divide among behaviorists that has existed for years over whether nature or environment is most important in shaping behavior. That affects whether you support or deny the implications of this experiment.

The researcher built Rat Park used the assumption that caged animals were miserable. Using 2 sets of rat enclosures - the old cages and another was a very large plywood box with plenty of room for rats to play and have their own space - That was called Rat Park (or Rat Heaven by some). Far fewer rats died from the drugs than those in cages. Due to the current addiction scourge his work is resurfacing not without lots of room for interpretation and argument. Researcher comments here:

http://tinyurl.com/yd3xhn43