We shouldn't necessarily generalize findings in rats to behavior in humans, but this comic about a study done by Dr Bruce Alexander shows us that the line between addiction and non-addiction could run straight through one's place in the capitalist hierarchy - that it takes an imposed isolating system that drives counter to our natural desires for solidarity and community to enforce the possibility of addiction so severe that it can cause death.

The comic ends on a kind of dumb lib take that it's merely "seeing" oneself in a Rat Park or in the Cage for why some are addicted and others are not (instead of an analysis based on material conditions analogous to Rat Park or the Cage), but most of it is good.