Rat Park: Science Caper or Curio?

caruba via flickr, h/t to Joe Kloc

Funny that this was the thing that got me back to my blog after an extended hiatus (though I've got like 4 drafts 80% done in the pipeline, waiting for polish). Procrastination can work wonders.

My friend Ryan, a fellow neuroscience grad student working on reward, motivation, and addiction using a rat model, pointed me to this blog post. The writer is Tom Stafford, one of the two authors of the popular science book Mind Hacks, and a researcher at the University of Sheffield. The post recapped a series of studies conducted in the '70's by Bruce Alexander and colleagues at Simon Fraser University, in which they built their test rats a large, well-furnished playpen, then tried to replicate classic drug addiction studies.

What they found, as Stafford describes, surprised them -- the rats living socially in the open, enriching pen actually avoided drinking water laced with morphine, instead of consuming the drug to the exclusion of nearly all other behavior. Stafford also points readers to this comic by Stuart McMillen that illustrates the story. Stafford then concludes the post by musing, among other things, that "even addictions can be thought of using the same theories we use to think about other choices, there isn’t a special exception for drug-related choices."

Okay, so. We've got a lot of crazy ideas kicking around here, so let's take this slow.

First off -- while I haven't read Mind Hacks, Stafford appears to be a pretty accomplished researcher, and my default position is to be glad that people are writing fun science books unless and until I have reason to suspect they're doing more harm than good. After all, I wouldn't have heard about this if not for his post. McMillen's comics likewise seem fun and clever, and remind me of a more serious counterpart to nerdy staples like The Oatmeal or Saturday Morning Breakfast Cereal. (If you haven't seen these -- not to even speak of XKCD -- run, don't walk, to way funner and smarter nerd porn than anything I've done yet. Go ahead, close this tab.)

With that out of the way, I'm... not placated by the story here. There are a number of reasons for this. In order of increasing discomfort, here they are:

(Note: apologies for linking to academic papers. I know many would-be readers don't have access to them. If you're affiliated with a University, try searching for them using your library's website; if not, try to reach out to somebody you know who is.)

1. While the role of context and social structure in drug abuse is still not a big enough issue, it isn't anything new either. Drug addicts who enter rehab clinics, get clean, then go right back to their old stomping grounds are surrounded by people and paraphernalia that remind them of their temptation, which can undo all their progress. Going beyond addiction, behavior of all kinds can be triggered almost automagically just by finding yourself in familiar settings -- as anybody who's moved and then started to drive home to the wrong house can attest. And I can't even begin to broach the social science literature on the influences of socioeconomic status, education, access to healthcare, etc. on propensity for drug use (here's just one example out of hundreds). So implying the ideas derived from this study should rewrite the rules on addiction is a sizable overstatement.
2. The biggest question-mark in this article, and the statement that I think needs the most gratuitous linkage, reads "There have been criticisms of the study’s design and the few attempts that have been made to replicate the results have been mixed" [emphasis added]. The fact that literally the subsequent sentence hand-waves that away -- "Nonetheless the research does demonstrate that the standard “exposure model” of addiction is woefully incomplete," -- using such strong language to criticize a whole field seems, to me at least, way off-base. You don't say a model (even a simple one constituting only part of prevailing theories on drug use) is "woefully incomplete" because of a 40-year-old paper with replicability issues, and you certainly don't say that without at least pointing readers to those attempts to replicate.*
3. To say that rats could be put in any environment where they'd stop taking drugs entirely, given a choice and even encouragement, is a seriously bold claim; or at least it is today. In the decades since those studies were conducted, rats have been -- beg pardon, for folks who have concerns about the ethics of animal research -- tested on every drug under the sun and given practically any task imaginable, and a huge portion of those results have translated pretty well into human findings. An entire literature has emerged on the science of reward and addiction, a field in which Ryan and his mentors, Brian Baldo and previously Kent Berridge, are participants. And we've got pretty solid ideas about the systems in the brain where these behaviors are generated. So it would require more than a little replication to validate those claims.
4. Most unsettlingly, there seem to be some oddities about the experiments and the way they're being presented. Correct me here, dear readers, if I missed something.

• In McMillen's comic, he writes that Alexander et al. "covered the floor with fragrant cedar shavings for the rats to nest in". When Ryan and I read that, we Macaulay Culkin'd so hard: cedar is toxic.



quicheisinsane via flickr

• Here's an example of one such finding. A 1997 review of bedding materials in labs around the world found that pine shavings were extremely cytotoxic compared to corncob, straws and other materials. In fact, a paper published as early as 1968 -- that's almost a decade before the Rat Park experiments -- found cedarwood to be a bad environment. If it's true, then, that the bedding was cedar, then Houston, we have a problem.
• Even more confusing, the paper linked to in Stafford's post said the floor of the pen was sawdust -- different, but still linked with a few major respiratory problems. So was McMillen reading a different paper? Did the research team use different bedding systems in their different studies? It looks like the latter, based on this 1981 study that mentions cedar shavings. (Once again, though, since I'm not an expert I don't know how these problematic conditions would affect the results; they just add a lot of uncertainty, and speak to the possibility that there were unaddressed or as-yet-unknown problems in their methods.)
• *For the interested, here's a thesis published in 1985 that suggests that "during a colony conversion the supplier inadvertently introduced strain differences making the present rats more resistant to xenobiotic consumption." It's only one non-replication, but even so I didn't have an easy time finding it.

So in general, the post made me a little uncomfortable at times, and the study did too. When it comes to a topic as stigmatized as drugs, there are always people with pet opinions looking for validation; so while nobody should be hushed, everybody should try to speak carefully. Implying that we can think of drug use as a totally non-compulsive act, and therefore subject to the same moral culpability as all other actions, is a proposition the neuro and psych communities have spent years and years trying to overcome. Drug courts, which have experienced so much success as alternatives to prison, were only made possible by thinking about addiction as a problem to fix, not a sin to punish.

To say otherwise -- to put all that progress at risk -- should not be done lightly.