an example of the complexity of dopamine: a study allowed animals to self-administer cocaine. Other animals were administered the drug in the brain on the same schedule but without 'choosing' to take it. The findings showed that the areas of the brain affected differed depending on these two conditions. This is a study with rats, and yet the effects of a seemingly small environmental/psychological difference changed everything

Another study on electrical brain stimulation showed that while animals would self-administer it, when it was automatically administered, the same animals would respond always to turn it off