I've heard this said .. admittedly, deep within the bowels of many a coffeeshop .. of marijuana.

Basically, weed rewards us for its continued safe domestication.

Try as I might, I cannot find a way to disprove this theory. The more I test it, the more it seems absolutely correct.

The same of course, is true of coffee and tobacco, albeit the means of domestication differ in magnitude and effect in each case.

The jury is still out on Triffids, however.