All human societies use mind-altering substances: caffeine (coffee, tea, coca-cola, etc.) alcohol (wine, beer, vodka, etc.), sleeping pills, antidepressants, opioids, marijuana, mushrooms, cocaine, amphetamines, etc.

We – homo sapiens –  consider ourselves rational. Colloquially, “rational” has several meanings. It can describe a thinking process based on an evaluation of objective facts (rather than superstition or powerful emotions); a decision that maximizes personal benefit; or simply a decision that’s sensible. In this article, the first definition applies: Rational decisions are those grounded on solid statistics and objective facts, resulting in the same choices as would be computed by a logical robot.

Tverski and Khaneman have been shown that our brain is more heuristic than rational.

But even if it was a perfect rational machine, how can  it produce rational choices if we “alter” our brain status and thinking process daily with psychoactive drugs? 

In 1948, zoologist H. M. Peters was apparently pretty annoyed by the fact that garden spiders build their webs from 2am-5am, and he asked pharmacologist Peter N. Witt to drug them and see if he could get them to start building their webs earlier. So, Witt began researching the effect psychoactive drugs had on spiders and made a very interesting discovery. None of the tested drugs changed the time of day that spiders built their webs, but they did greatly affect the size and shape of them.
Amphetamine, mescaline, strychnine, LSD, and caffeine were used in the tests, and all of them had a negative effect on the regularity of the web circles- except one: LSD. 
In small doses, LSD actually made the circles around the web more regular. Amphetamine only caused slight irregularities, but caffeine is a different story. Caffeine caused severe alterations to the web structure, as seen in the picture below.


Caffeine, one of the drugs most commonly consumed by humans, made spiders practically incapable of doing the web.

Caffeine and related methylxanthines (theobromine and theophylline for examples) – that  are natural  pesticides developed by plants as protection against worms – are present in coffee, chocolate, tea.

The only drug,  worse than caffeine, was the sleeping pill (Chloral Hydrate).