The effects of psilocybin on primary process content in language.

The hypothesis that psilocybin induced primary process thinking was assessed. On four separate occasions, a subject was asked to write before, during, and after the hallucinogenic experience induced by doses ranging between 80 and 200 microgram/kg of psilocybin. Texts produced at the drug peak contained significantly more primary process content and were significantly more stereotyped on several measures than those written before or after the drug peak.