What Was The Good Friday Experiment?

The Good Friday Experiment was the first empirical study to discover that psilocybin could produce mystical experiences — despite being somewhat flawed.

Sam Eskenazi Last Updated: April 13, 2022 Print

Can psilocybin, the active ingredient in magic mushrooms, induce spiritually significant experiences? 

This is the question theology student Walter Pahnke, and his team at Boston University sought to answer during the Good Friday Experiment. 

Under the guidance of Timothy Leary and Richard Alpert, and the rest of the Harvard Psilocybin Project, a study was set up to put it to the test. 

What did the study find? What makes it so significant? And why is this study so controversial today?

What Was The Good Friday Experiment?

The Good Friday Experiment (sometimes referred to as the Marsh Chapel experiment) was a test conducted in 1962 by a group of theology students at Harvard Divinity School to see if psilocybin could be used to help encourage religious experiences.

The experiment was led by Walter N. Pahnke and supervised by members of the Harvard Psilocybin Project. 

The study was nicknamed “The Good Friday Experiment” because it occurred on Good Friday. The purpose of the experiment attempted to determine if magic mushrooms could reliably induce religious experiences. 

The basis of the experiment was in the well-studied use of psychedelics in other types of religious practices, most notably within the religious practices associated with shamanism

Native Americans were well known to use peyote (a natural source of mescaline) to achieve spiritual experiences, so the researchers wanted to see if they could experience the same effects using psilocybin from magic mushrooms instead [1].

So, how did the experiment work?

The GFE Was Led By Walter Pahnke

Study Design: How The Good Friday Experiment Worked

The goal of the experiment was to determine whether or not psilocybin could “induce” a mystical experience. The researchers decided that the easiest thing to do would be to take fellow religious student volunteers and dose them with magic mushrooms.

The experiment used two groups of divinity student volunteers, divided into two groups, with half being given psilocybin and the other half only receiving niacin (vitamin B3). The niacin in the placebo provided a flushing feeling in the face. Researchers thought this would make it less obvious to the participant that they were given the placebo control. 

After dosing, the subjects were monitored, and their responses to how they felt were compared on a questionnaire to attempt to link the sensations that the subjects were experiencing. 

What is the Mystical Experience? 

Mystical experience is defined as any experience that challenges one’s ontological understanding of the world. These experiences are often (but not always) interpreted as an encounter with the divine and are especially meaningful or profound. 

Often, these experiences are so far outside of our normal comprehension of life and experience that we cannot fully describe them with rational language. 

The Good Friday experiment tried to assess individual subjects’ mystical experiences based on eight distinct categories: 

  1. Unity, both internal and external
  2. Transcendence of time and space
  3. Deeply felt a positive mood
  4. Sacredness
  5. Objectivity and reality
  6. Paradoxicality
  7. Alleged ineffability
  8. Transiency

Pahnke and the researchers hypothesized that, by quizzing their subjects on questions focused on each of these categories, their overall mystical experience could be evaluated.

Results: What Were the Findings of the Good Friday Experiment?

The Good Friday experiment is one of those experiments with a bit of a dubious history when it comes to interpreting the results.

Pahnke assessed the study by having the participants fill out a questionnaire that quizzed them on their subjective experiences, with questions focusing on such categories as “Unity” and “Deeply Felt Positive Mood.”

After the experiment, the average score throughout all of the categories on the questionnaire among those dosed with psilocybin was 60.8%, versus only 11.8% for the control group. 

While the experiment’s results stated that psilocybin could definitely have uses in encouraging religious experiences, more modern researchers have cast significant doubt on the integrity of this experiment [2].

Criticism: Why Was The Good Friday Experiment Flawed?

Despite the seemingly positive results of the Good Friday Experiment, the methodology and scientific integrity of the experiment left a lot to be desired.

So, what is it about the experiment that makes it flawed? 

1. The Study Was Not Properly Double-Blinded

The main issue of the Good Friday experiment, at least with regard to its scientific credibility, is the fact that the double-blind nature of the experiment was broken.

As Rick Doblin, the founder of MAPS (Multidisciplinary Association for Psychedelic Studies), points out in his critique of the experiment, the effects of the placebo niacin wore off after only an hour or two — whereas the effects of the psilocybin actually increased in intensity after a few hours [3]. This made it obvious which group the participants were placed in, thereby affecting the outcome. 

This meant that, despite the efforts of the researchers, the subjects knew whether or not they had been dosed with psilocybin, altering the results thanks to their perception of the drugs.

The entire purpose of conducting studies using a double-blind protocol is to resist the effects of a unique phenomenon that can synthetically alter the outcomes of a study: the Rosenthal effect.

The Rosenthal effect is the tendency for the expectation of a particular outcome to affect that outcome. 

This is also known as the experimenter expectancy effect and essentially means that if a researcher believes that a particular effect will be reached, they will conduct their research and study in such a way as to try and guarantee that result, even if it is not a conscious decision.

You can mostly eliminate this problem by conducting an experiment in a double-blind manner. This means that both the researcher and the subjects do not know if they are receiving the tested substance or a placebo, something that the Good Friday experiment failed to do. 

2. The Questionnaire Was Too Vague

To gather the data, the researchers in the Good Friday Experiment conducted a 100 question questionnaire among the subjects, both those that were dosed with psilocybin and those that took the placebo.

The problem with using a questionnaire to gather data from subjects is that there is always the issue of subjectivity among the subjects, as well as the questions having an inherent bias.

For example, the Good Friday experiment’s questionnaire included questions to do with “a sense of unity” and how much they experienced “transiency.”

These terms are obviously very easy to confuse and misinterpret. This is especially problematic for people of a religious disposition, especially because the experiment itself was trying to determine if psilocybin could produce truthful religious experiences.

A great example of this confusion is the critiques raised by R.C Zaehner, who attested that, because the questionnaire contained no specific references to Christianity, it was impossible to determine if what the subjects were feeling were truly religious because they would not be able to identify a specific experience with Jesus Christ [4].

In his opinion, that was the only way a religious experience would be valid.

3. Researchers Omitted Negative Findings

One massive issue with the experiment, and the results that researchers took away from it, is that they failed to include negative consequences as part of their results.

While they generally found that all of those dosed with psilocybin had a religious experience, they did not take into account the fact that many of the participants actually reported negative feelings.

Some of the participants reported that they were feeling weak or that they believed they were dying.

In fact, one subject actually had to be physically restrained from leaving the church where they were conducting the experiment. He believed that he was the reincarnation of the messiah and needed to be released to spread the word of God. He actually had to be dosed with a sedative to calm him down.

Despite the fact that the participant did indeed experience a religious experience, he still overwhelmingly had a negative experience, which was not really taken into account by the experiment.

Did The Good Friday Experiment Show That Psilocybin Can Be Useful For Religious Experiences?

When considered solely from the perspective of the data that the Good Friday experiment reported, it would appear that the experiment was pretty much a success.

Based on the questionnaire and the interpretations of data among the researchers, the study reported that all of those dosed with psilocybin experienced what they classified as a religious experience.

Based on that result, the experiment states that it provides empirical support for the notion that psychedelic drugs may be a reliable way of facilitating a religious experience.

In fact, one of the participants of the study, Huston Smith, later went on to be a widely published theological researcher, who frequently cites the experience of being given psilocybin as part of the experiment as profoundly positive to his religion [5].

Can We Trust The Results Of The Good Friday Experiment?

The most frequent problems with many studies, no matter their time period or what they are about, are a lack of a large enough sample size and poor scientific methodology.

Critics of the Good Friday experiment commonly state that these problems are definitely present, which certainly casts doubt on the results.

However, just because the scientific methodology is inadequate doesn’t mean that the study deserves to be totally discounted.

Even though the researchers failed to account for many things and underreported the full extent of the experiences of their subjects, there is still useful information in their data.

For one thing, it demonstrated the effectiveness of psilocybin in terms of its efficacy in creating a psychedelic high. For many people, there simply wasn’t any research or evidence to suggest that the effects of psilocybin were significant or useful.

The other significant quality of this study that makes it worth understanding is the fact that it happened to begin with.

Follow-up Experiments: Roland Griffiths & John Hopkins University

The Good Friday experiment isn’t the only example of a study into psilocybin, nor will it be the last.

Researcher Roland Griffiths and John Hopkins University conducted a follow-up experiment using modern scientific methods, including double-blinding and multiple sessions [6].

The use of multiple sessions allowed for essentially repeated examination of the subjects when under the influence of the drug. This allowed for participants’ reactions and responses to the drug to be compared over multiple sessions, creating a broader picture of the results.

Another positive aspect of this experiment compared to the Good Friday Experiment is that the participants were each tested individually rather than in the wider group setting of the Good Friday experiment. This meant that the participants could not influence one another, meaning that their responses were more individual and less likely to be tainted by a group setting.

Interestingly, this follow-up experiment noticed similar results as the Good Friday Experiment, though it also found that a number of the participants reported experiencing significant anxiety during their doses.

However, the overall results were positive, with the volunteers rating the psilocybin experience as a positive thing and being of extreme spiritual significance, as well as generally having a positive change in their behavior and outlook on life. 

Why The Good Friday Experiment Is Still Relevant Today

Despite all of the valid criticisms of the study, the Good Friday Experiment is still well studied and cited to this day. It was the first study of its kind to use psychedelics as a means of studying consciousness and cosmic experience. 

As psilocybin, and indeed all psychedelic drugs, were outlawed shortly after the experiment, the Good Friday Experiment remained one of the best studies available regarding psychedelic drugs for decades. 

The experiment might have a lot of flaws, but it demonstrated scientifically that psilocybin could indeed be linked to religious experiences.

No matter the inherent qualities of the study, it demonstrates that psilocybin had practical, empirical uses, and it helped to legitimize psilocybin over the long term.


  1. Winkelman, M. J. (2021). The evolved psychology of psychedelic set and setting: Inferences regarding the roles of shamanism and entheogenic ecopsychology. Frontiers in Pharmacology, 12, 115.
  2. Pahnke, W. N. (1963). Drugs and mysticism: An analysis of the relationship between psychedelic drugs and the mystical consciousness: A thesis (Doctoral dissertation, Harvard University).
  3. Doblin, R. (1991). Pahnke’s “Good Friday experiment”: A long-term follow-up and methodological critique. Journal of Transpersonal Psychology, 23(1), 1-28.
  4. Zaehner, R. C. (1973). Zen, drugs, and mysticism. New York: Pantheon Books.
  5. Smith, H. (2000). Cleansing the doors of perception: The religious significance of entheogenic plants and chemicals. Tarcher, Putnam.
  6. Griffiths, R. R., Richards, W. A., McCann, U., & Jesse, R. (2006). Psilocybin can occasion mystical-type experiences having substantial and sustained personal meaning and spiritual significance. Psychopharmacology, 187(3), 268-283.