The Shulgin Rating Scale

Dr. Alexander Shulgin is a well known biochemist who discovered hundreds of novel psychedelics and developed a simple scale for the measurement of the subjective effect of psychoactive substances at a given dosage. This scale was known as the Shulgin Rating Scale and defined as a five tier leveling system of description.

The following is an excerpt from Shulgin's book, PiHKAL. It should be understood that Shulgin is not rating the drug itself, but the quality of his specific experience with the drug (which can be influenced by set and setting).

Over the years, I evolved a method of assigning symbols which refer exclusively to the perceived strength or intensity of the experience, not to the content, which is evaluated separately in my research notes. It could just as well apply to other classes of psychoactive drugs, such as sedative-hypnotics or anti-depressants. I use a system of five levels of effect, symbolized by pluses and minuses. There is one additional level I will describe, but it stands by itself, and is not comparable to the others.

MINUS (-)
There is no effect noted, of any nature, which can be acribed ot the drug in question. This condition is also called "baseline," which is my normal state. So, if the effect of the drug is minus, it means I am in exactly the same state of mind and body I was in before taking the experimental drug.

PLUS - MINUS (+/-)

I am feeling a move off baseline, but I can't be absolutely sure it's a drug-effect. There are a lot of false positives in this category, and often my report concludes that what I interpreted as signs of activity were, in fact, products of my imagination.

Here, I will describe briefely something called the "alert." It is some small sign which serves to remind me (in cases I have become distracted by phone call or conversation) that I had, indeed, taken a drug. It comes early in the experiment, and is the prelude to further developments. Each member of our research group has his own individual form of alert; one notes a decongestion of the sinuses, another has a tingling at the back of the neck, still another gets a brief runny nose, and I, personally, become aware that my severe tinnitus has disappeared.

The level of effectiveness of a drug that indicates a threshold action. If a higher dosage produces a greater response, then the plus/minus (+/-) was valid. If a higher dosage produces nothing, then this was a false positive.

PLUS ONE (+)

There is a real effect, and I can track the duration of that effect, but I can't tell anything about the nature of the experience. Depending on the drug, there might be early signs of activity, which can include nausea, even active vomitting (although these are extremely rare). There could be less disturbing effects, such as lightheadedness, compulsive yawning restlessness, or the wish to remain motionless. These early physical signs, if they arise at all, usually dissipate within the first hour, but they must be considered real, not imaginary. There can be a mental change, but it is not definable as to character. There are seldom false positives in this category.

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 (++)
The effect of the drug is unmistakable, and not only can its duration be perceived, so can its nature. It's at this level that the first attempts at classification are made , and my notes might read something like this: "There is considerable visual enhancement and much tactile sensitivity, despite a light anaesthesia." (Which means that, although my fingertips might be less than usually responsive to heat or cold or pain, my sense of touch is definitely hieghtened.) At a plus-two, I would drive a car only in a life-or-death situation. I can still answer the phone with ease, and handle the call competently, but I would much prefer not to have to do so. My cognitive faculties are still intact, and if something unexpected should arise, I would be able to suppress the drug effects without much difficulty until the problem had been taken care of.

It's at this stage, plus-two, that I usually bring in another experimental subject, my wife, Ann. The effects of the drug are distinct enough at this level for her to be able to evaluate them in her own body and mind. She has a metabolism quite unlike my own, and of course a very different mind, so her reactions and responses constitute important information.

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 (+++)

This is the maximum intensity of drug effect. The full potential of the drug is realized. Its character can be fully appreciated (assuming that amnesia is not one of its properties) and it is possible to define th chronological pattern exactly. In other words, I can tell how soon I get an alert, when the transition stage ends, how long the plateu-- or full activity-- is in effect before I sense the beginning of a decline, and precisely how steep or gentle the decline to baseline is. I know what the nature of the drug's effects are on my body and mind. Answering the phone is out of the question, simply because it would require too much effort for me to maintain the required normalcy of voice and response. I would be able to handle an emergency, but suppression of the drug effects would require close concentration.

After Ann and I have explored the plus-three range of the new drug, establishing the range of dosage levels at which we get this intensity of effect, we call the research group together and share the drug with them. It is after the members of the rresearch group have submitted their reports on the experience that the synthesis of the neww drug and its human pharmacology is ready to be written up for inclusion in a scientific publication.

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 (++++)

This is a separate and very special category, in a class by itself. The four pluses do not imply in any way that it is more than, or comparable to, a plus-three. It is a serene and magical state which is largely independent of what drug is used-- if any drug at all -- and might be called a "peak experience," in the terminology of the psychiatrist, Abe Maslow. It cannot be repeated at will with a repetition of the experiment. Plus-four is that one-of-a-kind, mystical, or even religious experience which will never be forgotten. It tends to bring about a deep change of perspective or life-direction in the person who is graced with it.

A rare and precious transcendental state, which has been called a 'peak experience', a 'religious experience,' 'divine transformation,' a 'state of Samadhi' and many other names in other cultures. It is not connected to the +1, +2, and +3 of the measuring of a drug's intensity. 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.

-- PiHKAL, Alexander Shulgin