Shulgin Rating Scale


The Shulgin Rating Scale is a simple scale for reporting the subjective effect of psychoactive substances at a given dosage, and at a given time.

The system was developed for research purposes by the American biochemist Alexander Shulgin and detailed in his book ‘PiHKAL’ (‘Phenethylamines I Have Known And Loved: A Chemical Love Story’).

PLUS ONE (+) The drug is quite certainly active. The chronology can be determined with some accuracy, but the nature of the drug’s effects are not yet apparent.

PLUS TWO (++) Both the chronology and the nature of the action of a drug are unmistakably apparent. But you still have some choice as to whether you will accept the adventure, or rather just continue with your ordinary day’s plans (if you are an experienced researcher, that is). The effects can be allowed a predominant role, or they may be repressed and made secondary to other chosen activities.

PLUS THREE (+++) Not only are the chronology and the nature of a drug’s action quite clear, but ignoring its action is no longer an option. The subject is totally engaged in the experience, for better or worse.

PLUS FOUR (++++) A rare and precious transcendental state, which has been called a ‘peak experience,’ a ‘religious experience,’ ‘divine transformation,’ a ‘state of Samādhi,’ and many other names in other cultures. It is a state of bliss, a participation mystique, a connectedness with both the interior and exterior universes, which has come about after the ingestion of a psychedelic drug, but which is not necessarily repeatable with a subsequent ingestion of that same drug. If a drug (or technique or process) were ever to be discovered which would consistently produce a plus four experience in all human beings, it is conceivable that it would signal the ultimate evolution, and perhaps the end, of the human experiment.

Shulgin Ratings typically include four components. An identification of the chemical being ingested, a dosage, and a descriptive narrative including the ratings themselves used to describe various moments in time. The chemical itself must be clearly identified, preferably using chemical nomenclature, as opposed to popular or ‘street’ names. The dosage must be known and communicated, as substances may result in wildly different ratings at different doses. The rating itself gives a comparable value relating to the subjective intensity of the experience, including auditory, visual, emotional, mental, physical and other sensory effects. The narrative may include various Shulgin ratings, noting the time to achieve various levels:

‘(with 22 mg) A slow onset. It took an hour for a plus one, and almost another two hours to get to a +++. Very vivid fantasy images, eyes closed, but no blurring of lines between ‘reality’ and fantasy. Some yellow-grey patterns a la psilocybin. Acute diarrhea at about the fourth hour but no other obvious physical problems. Erotic lovely. Good material for unknown number of possible uses. Can explore for a long time. Better try 20 milligrams next time.’

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