In medical terminology, addiction is a state in which the body relies on a substance for normal functioning and develops physical dependence. This is what you might call a "chemical" addiction - that is, if you're addicted to a substance, your body has altered its natural processes to require whatever substance you're addicted to. Substance abuse, a.k.a. 'drug use', is presumed to fall under this classification because sudden removal of said drug causes "withdrawal" and a characteristic set of signs and symptoms. New research, however, shows that drug addiction is not purely chemical.
The basic idea of the study, conducted by the U.S. DOE's Brookhaven National Laboratory, was to determine if cocaine addicts were more drawn to images of cocaine and cocaine use than non-addicts. To do this they set up a set of four decks of cards - one with more "positive" images, one with "negative" images, one with "neutral" images, and one with "cocaine" images. Subjects were unaware of the decks' content, and were asked to select one of four face-down card decks. They then were told to choose from the same deck or another. This test of choice is considered 'implicit' because subjects were not necessarily aware of their tendency to choose one type of image over the others. Then subjects underwent an 'explicit' choice task where they repeatedly selected between two side-by-side, face-up images taken from the four decks.
On both tasks, the cocaine-addicted individuals chose the 'cocaine' images more than the controls, who showed clear aversion to these images. Even more interestingly, the cocaine addicts seemed somewhat unaware of their bias. They rated rated pleasant images as 'more pleasant' than the cocaine-related images, but at the group level still chose from these two picture categories at the same rates on both tasks. This means they may not be fully aware of their choices or that addiction may not be completely driven by pleasure-seeking, as generally assumed.
"This behavioral study demonstrates for the first time that drug-related choice in cocaine addiction extends to abstract, non-pharmacological stimuli, facilitating the study of choice behavior in addiction without using actual cocaine," said Scott Moeller, the graduate student who presented the results at the Society for Neuroscience annual meeting in Washington D.C..
Another important find was that cocaine addicts individuals with the greater preference for cocaine-related images had used cocaine more frequently in the previous month - so it's possible that tasks like these could be used as an objective measure of the severity of drug use which is otherwise measured by self-reporting.
This study, to me, shows that even drug addiction isn't just chemical. Clearly there is a psychological component that is either present before or because of the drug. Of course, this component may be 'biological' in nature (like the study which found cocaine addicts had thinner cortexes in their brains). It all stills brings up the 'chicken' or the 'egg' argument - are people addicts because they are dependent on drugs or were they already predisposed to drug use before ever touching an illegal substance? It's even possible that further studies in the nature of addiction may make it possible for the regulation and legalization of drugs.