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Other researches have tried and failed to reproduce Rat Park's results:


"The results of earlier research, indicating rats housed in a quasinatural colony drank significantly less sucrose-morphine than rats isolated in standard laboratory cages, could not be replicated"

The research you mentioned specifies in the abstract a probable cause for failing to replicate the same conditions for the experiment: It is possible that during a colony conversion the supplier inadvertently introduced strain differences making the present rats more resistant to xenobiotic consumption.

In my opinion this tells a lot.

BTW: There are other researchers that replicated similar results on similar experiments too: http://www.ncbi.nlm.nih.gov/pubmed/11072395?dopt=Abstract

So is better to see all the experiments to avoid bias.

Why? What they're suggesting is that the genetic markup of the rats made the difference (that's what strain differences mean), not the environment.

And your other linked experiment isn't at all similar and doesn't have similar results. It's not even about opiate addiction.

Btw, Bruce Alexander is still alive and it wouldn't be that hard for him to find the funding to replicate his experiment, with better controls, if he wanted to.

The two followup studies do disagree with the original Rat Park experiment, but I think you inadvertently misrepresent their results by cutting off your quote mid-sentence.

> The results of earlier research, indicating rats housed in a quasinatural colony drank significantly less sucrose-morphine than rats isolated in standard laboratory cages, could not be replicated, as the consumption of sucrose-morphine by the isolated animals in the present two studies was reduced. [emphasis added]

Without that last bit, the reader is left with the impression that all rats were highly addicted regardless of their environment, but the results were the opposite. All rats were less addicted than expected, regardless of their environment. Again, you're correct that the updated studies refute the original, but I feel like that distinction is important in a discussion that centers around addiction more than just the Rat Park experiment.

Additionally, the abstract notes that the latest studies may have been biased by a strain of rats that is less prone to addiction that those used by the Rat Park study. You noted in another reply that this indicates genetics play more of a role in addiction than environment, but this also calls into question any inferences about human addiction that are based on rat studies which do not include an analysis of the specimens' genetic predisposition toward addiction.

Finally, research that supports the result of the Rat Park does exist [1]. Studies have found isolated mice are less resistant to addiction compared to those living in stimulating and social environments [2][3]. Another study found that rats isolated in key parts of their development are more prone to alcohol and amphetamine addiction in adulthood [4]. Based on the latter example, the effects of environment on addiction may be more nuanced that the Rat Park experiment would suggest.

[1] http://en.wikipedia.org/wiki/Rat_Park#Related_research

[2] http://www.sciencedirect.com/science/article/pii/S0014488607...

[3] http://www.jneurosci.org/content/23/35/10999.full

[4] http://www.utexas.edu/news/2013/01/23/socially-isolated-rats...

I'll readily admit that studies that show sad rats to more easily get addicted to morphine exists and that they are valid. But they are a far cry from the amazing results the Rat Park study achieved. In the comic, addicted happy rats would rather suffer physical withdrawal symptoms than drinking sugar-morphine water. It's the difference between "environment may have an impact" and "the environment's impact is so huge that it overshadows everything else by a wide margin."

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