Carl Sagan, Cannabis, and the Right Brain Hemisphere

Carl Sagan and the outline of a brain split into two halves

Carl Sagan speculated that the acute effects of cannabis lead to a pronounced right hemisphere style of cognition. Functions such as creativity, pattern recognition, insight and episodic memory are strongly supported by the right hemisphere. Now, 40 years later, does modern research support Sagan’s hypothesis?

What it comes down to is that modern society discriminates against the right hemisphere.

Roger Wolcott Sperry (1913-1994), neuropsychologist and neurobiologist, known for his revolutionary studies of split-brain patients

In 1971, Harvard Prof. Lester Grinspoon published his milestone book „Marijuana Reconsidered“, in which he featured an essay “Mr. X” by his best friend, the famous astronomer and science popularizer Carl Sagan. [1] 

In his essay, Sagan reports that for him, the marijuana high led to various cognitive enhancements, including an enhancement of cognitive abilities like enhanced episodic memory, pattern recognition, creativity, and the ability to produce insights. Sagan’s essay “Mr. X” is still one of the most illuminating accounts on the positive mind-altering potential of the marijuana high.

I have extensively examined the phenomenon of insights and other cognitive enhancements during a marijuana high from a modern neurophilosophical perspective and think that Sagan’s observations are accurate and ground-breaking.

Many other cannabis users before and after Sagan have described similar mind enhancements during a high.

My own experiences with the marijuana high had been very similar, and my research aims to explain how marijuana can induce insights and many other cognitive enhancements, given that good quality cannabis is used by skilled users. [2]

Sagan’s hypothesis

Sagan was so excited about the cognitive enhancements he experienced with marijuana that he used it a lot to come to insights for his work. His biographer Keay Davidson wrote that when Grinspoon received unusual high-quality marijuana from an admirer by mail, he shared the joints with Sagan and his wife Ann Druyan. “Afterward, Sagan said, ‘Lester, I know you have only got one left, but could I have it? I’ve got serious work to do tomorrow and I could really use it.” [3]

Sagan was famous – or, for many of his academic colleagues, infamous – for making brilliant but daring speculations – not only in his field of astronomy, but also in other scientific fields. As his biographer Keay Davidson remarks, Sagan for instance wrongly predicted the existence of complex organic molecules on the moon; but, Davidson adds, “(a)s it turned out later, complex organic molecules pervade much of the outer solar system and beyond.” [4]

In his Pulitzer price-winning book “The Dragons of Eden – Speculations on the Evolution of Human Intelligence”(1977), Sagan introduced a survey of what  cognitive and evolutionary scientists had to say about the evolution of the human mind and presented many of his own brilliant speculative ideas on the nature and evolution of human intelligence. Sagan also introduced a speculative thesis about the effects of marijuana on the human brain. He started from an analogy made by psychologist Robert Ornstein:

“He {Ornstein} suggests that our awareness of right hemisphere function is a little like our ability to see stars in the daytime. The sun is so bright that the stars are invisible, despite the fact that they are just as present as they are in the daytime as at night. When the sun sets, we are able to perceive the stars. In the same way, the brilliance of our most recent evolutionary accretion, the verbal abilities of the left hemisphere, obscures our awareness of the functions of the intuitive right hemisphere, which in our ancestor must have been the principal means of perceiving the world.” [5]

In a now famous footnote to this paragraph Sagan formulates his hypothesis on how a marijuana high could affect thinking:

“Marijuana is often described as improving our appreciation of and abilities in music, dance, art, pattern and sign recognition and our sensitivity to nonverbal communication. To the best of my knowledge, it is never reported as improving our ability to read and comprehend Ludwig Wittgenstein or Immanuel Kant; to calculate the stresses of bridges; or to compute Laplace transformation. (…) I wonder if, rather than enhancing anything, the cannabinols (the active ingredient in marijuana) simply suppress the left hemisphere and permit the stars to come out. This may also be the objective of the meditative states of many Oriental regions.” [6]

Enhancements and suppression

Let me distinguish two aspects of Sagan’s hypothesis: First, there is the observation that a marijuana high leads to a style of cognition which cognitive scientists consider to be predominantly based in the right hemisphere. Second, Sagan speculates that a marijuana high might suppress left hemisphere functions and, therefore, lead to what we could call “right hemisphere thinking”.

Sagan’s hypothesis was based on his knowledge of what current science had to say about the human brain and the different style of cognition in the left and right brain hemispheres, as well as on his own experiences with marijuana.

Sagan’s claim reconsidered

During his lifetime, Sagan did not reveal to the public that he was a user of marijuana. In isolation, Sagan’s footnote about marijuana and its possible effect on the brain hemispheres seems to be a spontaneous speculation out of nowhere. Yet, when reading Sagan’s essay “Mr.X”, it becomes clear that Sagan’s experiential basis for such a claim was actually quite broad.

In his essay, he describes in some detail not only the enhancements mentioned in his footnote, but he also mentions other cognitive enhancements, such an enhanced ability to remember past events and to obtain deep insights. Also, like some other users before him, Sagan mentions that during a high, he also experienced enhanced

”perceptions of real people, a vastly enhanced sensitivity to facial expressions, intonations, and a choice of words which sometimes yields a rapport so close it’s as if two people are reading each other’s minds.” [7]

Sagan already knew that all of the cognitive enhancements he had described for a high would concern functions which cognitive science at the time found to be predominantly located in the right brain hemisphere; he had described the research concerning split brain patients and more on the pages preceding his hypothesis in “The Dragons of Eden”.

Sagan did not only know this research and did not only have his own knowledge about cognitive enhancements during a high, but he was also well acquainted with his friend Lester Grinspoon’s research about marijuana as a medicine and about its mind-enhancing potential. As Lester Grinspoon told me in private conversation, Carl Sagan had carefully read and commented upon his manuscript of “Marijuana Reconsidered”, in which Grinspoon extensively featured reports of other users who had described similar mind enhancements.

Carl Sagan giving a speech to an audience

Sadly, Sagan died in 1996, too early to witness the revolutionary discovery of the endocannabinoid system. Since then, we have learned about the amazing range of its physiological and cognitive functions. So, can we actually find evidence for or against Sagan’s hypothesis for instance looking at the distribution of endocannabinoid receptors (especially the CB-1 receptor, on which the exogenous THC acts)?

Sagan’s thesis and the endocannabinoid system

As far as I can see, there does not seem to be extensive research what concerns lateralization and the role of endocannabinoid signalling for higher cognitive functions. One often cited study found an increased blood flow in parts of the right hemisphere during a high [8], but another study states that “relatively high concentrations of cannabinoid receptors were consistently seen in cortical regions of the left (dominant) hemisphere, known to be associated with verbal language functions.“ [9]

The brain split in half with one side showing logic and the other creativity

It seems much too early to draw conclusions from brain imaging studies to evaluate Sagan’s hypothesis. Marsicano and Kuhner remind us that „sometimes the endocannabinoid system appears to be functionally important in regions or cell types where the density of CB1 receptor is relatively low {e.g. control of pain perceptions in the brainstem}.” [10] As far as I can see, we haven’t yet begun to understand how the endocannabinoids are involved in affecting different higher cognitive functions based in the left or right brain hemisphere.

Recent neuroscience and reports about the cannabis high

However, some more support for Sagan’s thesis seems to come from two other sources. First, Sagan’s description of the cognitive enhancements during a marijuana high have been described in detail by many more cannabis users. [11] The most impressive collection of recent anecdotal reports and essays about those enhancements comes from Sagan’s best friend Lester Grinspoon and can be found on his website

Second, if we look at what recent neuroscience has to say about differences in the cognitive functions and processing styles in the two brain hemispheres, Sagan still seems to have a point. From what we know now, the right hemisphere plays an important role for the cognitive processes named by Carl Sagan as enhanced during a high, as well as for many other enhancements described by other marijuana users.

In his book The Master and his Emissary. The Divided Brain and the Making of the Modern World, (2009), psychiatrist Ian McGilchrist gives a survey of the current scientific knowledge about the different styles of cognition in the left and the right brain hemisphere emerging from stroke cases in one hemisphere, split brain patient cases, and newer brain imaging studies.

According to McGilchrist, the right hemisphere is predominately involved in our ability to remember personal events (episodic memory), for associations between widely different concepts and ideas, complex pattern recognition, creative problem solving, insights, the appreciation of humor, the understanding of metaphors, self-awareness, the empathic understanding of others, the processing of words describing the mind, and the interpretation of emotional expression in faces, in intonation and verbal implications.

Also, the right hemisphere seems to be crucially involved in the interpretation of non-verbal communication and the perception of music. For the sake of brevity, I will leave it at this incomplete list, but actually, McGilchrist describes more cognitive functions as right hemisphere based; functions which also have been consistently reported to be enhanced during a high.

The effect of cannabis on attention

In general, then, it seems that research of the last forty years in the neurosciences lend some more support Sagan’s thesis that marijuana leads to an enhancement of right hemisphere-based cognitive abilities. One interesting puzzle, though, is one of the fundamental effects of marijuana on attention. During a marijuana high, we seem to ‘hyperfocus’. High users often get completely absorbed by the taste of ice-cream, by an intense stream of memories or ideas, or by the sensation of a kiss.

In other words, a high seems to cause a strong selective focus on whatever we attend to. According to McGilchrist, however, focussed attention is not a cognitive function performed primarily in the right hemisphere. Quite on the contrary, he summarizes the current research as saying that “(…) the right hemisphere is responsible for every type of attention except focused attention.” [12]

Evaluating Sagan’s hypothesis

So, when it comes to attention, at least one of the typical cognitive changes during a high does not seem to come from an enhancement of processes in the right hemisphere. Generally, then, while Sagan seems to have been basically on the right track with his hypothesis, not all of the cognitive enhanced functions during a high seem to be predominately based in right hemisphere activities.

We will have to wait for more research to be done in this field to see how exactly cannabis affects cognitive activities in the left and right brain hemisphere.

What about Sagan’s hypothesis that a high could suppress left hemisphere function and, thus, ‘bring out the stars’ and allow for an enhanced right hemisphere activity? As far as I can see, we are far from being able to tell whether the mind enhancements during a high observed by so many users come from a direct enhancement of certain cognitive functions, or whether they come from a suppression of some left hemisphere activities.

According to McGilchrist, the left and the right hemisphere are in a constant battle for control. In order to help us to survive, we and other animals need two conflicting systems of attention. He explains this point with the example of birds: to pick up seeds for food, a bird needs to narrowly focus on the seeds on the ground to motor control and coordinate food intake (left hemisphere function); but in order to survive, the bird has to get distracted by a predator like a fox or a falcon in the fringe of its perception.

A small blue and orange bird with a long beak sat on a branch

So there must be another type of attention drawing it to unusual new sensations (right hemisphere). Only the interplay of these competing attention systems located in the two brain hemispheres allows birds and other animals like us to survive.

Clearly, then, an enhancement of cognitive processes in one hemisphere could come from the suppression or weakening of cognitive functions in the other hemisphere. We still have to await further research to come to a better understanding on how consumed cannabinoids affect the endocannabinoid system and, generally, its role in higher cognition.

Yet, almost forty years after Sagan’s hypothesis, I think we can still say that he was on an interesting track. As far as I can see, we will only come to a better understanding of the nature of the high and its effects on attention, memory, pattern recognition, creativity, empathy, or insights, if we are beginning to research how endocannabinoids and consumed marijuana affects various cognitive processes in the left and the right brain hemisphere.

[1] Carl Sagan, „Mr. X“, in: Lester Grinspoon (1971), „Marijuana Reconsidered“, Harvard University Press, Cambridge, Massachussetts, p. 123 – 130. Sagan’s essay was published anonymously, Grinspoon revealed the identity of his author only years after Sagan’s untimely death.

[2] See Sebastian Marincolo (2010), „High. Insights on Marijuana“, Dogear Publishing Indianapolis, Indiana.

[3] Keay Davidson, (1999), „Carl Sagan. A Life.“, John Wiley & Sons, Inc., New York, p. 214.

[4] Ibid., p. 213.

[5] Carl Sagan (1977) „The Dragons of Eden. Speculations on the Evolution of Human Intelligence“, Random House Publishing Group, New York, p. 177

[6] Ibid.

[7] Carl Sagan, „Mr. X“, in: Lester Grinspoon (1971), „Marijuana Reconsidered“, Harvard University Press, Cambridge, Massachussetts, p. 127.

[8] Roy Mathew et al. (1997) , „Marijuana intoxication and brain activation in marijuana smokers“, Life Sci. 1997;60(23):2075-89.

[9] Glass, M., Dragunov, M., Faull, RL (1997) „Cannabinoid receptors in the human brain: a detailed anatomical and quantitative autoradiographic study in the fetal, neonatal and adult human brain.“ Neuroscience. 1997 Mar; 77(2): p. 299-318.

[10] Marsicano, G., and Kuner, R. (2008), „Distribution of CB1 Cannabinoid Receptors in the Nervous System“, in: Attila Köfalfi (ed.) (2008),  „Cannabinoids and the Brain“,  Springer Science and Business Media, New York, p. 164.

[11] Compare Sebastián Marincolo (2010), „High. Insights on Marijuana“, Dogear Publishing Indianapolis, Indiana.

[12] McGilchrist, Ian (2009), „The Master and His Emissary, The Divided Brain and the Making of he Modern World“, Yale University Press, New Haven and London, p. 39.

  • Disclaimer:
    This article is not a substitute for professional medical advice, diagnosis, or treatment. Always consult with your doctor or other licensed medical professional. Do not delay seeking medical advice or disregard medical advice due to something you have read on this website.


11 thoughts on “Carl Sagan, Cannabis, and the Right Brain Hemisphere”

  1. So i’m like reading The Master and His Emissary, and having a vape when it dawns on me that ganja is a right brain enhancer. Most everything McGilchrist says about the right brain points to cannabis as a magnifier of all that. Strange that so little has been mentioned about this. I just did a Google search for ‘cannabis as a right brain enhancer’ and got only one relevant article. This one! Most of the others were warnings about the I’ll effects of cannabis on the brain. So we’re still in the old world consciousness of marijuana being bad, but not too bad so it can be used recreationally like alcohol. It’s not like alcohol. And it has uses this left brained world doesn’t seem to want to acknowledge.

    1. Another clue to it’s right braininess is this.

      Before I go to perform a task, usually ones I do regularly, I often get high. What happens is I have a hard time in the beginning to get into gear because everything seems kinda novel like I haven’t done it countless times before. Novelty is a right brain speciality. So things go kinda slowly in the beginning. But an hour or so into the task, I have enough new information that the task can be accomplished by the left brain, and so I become very efficient at the task. It’s a good way to get new insights about things we do regularly, and god knows that is a good thing. It’s a great cure for boredom!!

    2. Sebastian Marincolo

      Thanks Tarun, I am glad to hear that you feel the same way. And yes, I am afraid it will take a while until we see more research on this – there is not much out there yet.

  2. I’ve stumbled upon this as I’m a regular user and I believe (similar to the comment above) without a doubt it helps me spiritually. I find cannabis enhances my ability to astral project, when using I find it really easy to push out of my body. Thanks for taking the time to piece all this info together, was a great read 👍

    1. Scarlet Palmer - Sensi Seeds

      Hi Onyxbeast,

      Thanks for your comment and kind words about this article! I hope you continue to enjoy the blog.

      With best wishes,


  3. Wauw that was very satisfying experience, i have just come from a private meditation session where i also vaporized some cannabis, and wanted so share my experience and express my gratitude to this article.

    First of all, im a former regularly user of cannabis, who used to have a moderate level/amount of intake, when i used/vaporized cannabis. (Meaning, i dont vape much when i do it, compared to most other users i know of).
    Now, i only use cannabis once in a while, (about 2 to 3 times a month). I have then started a practice where i sometimes vaporize some cannabis and meditate for a couple of hours thereafter.
    This night i had some insights, which led me to formulate a question which then led me to find this blog-article.
    And it was just so awesome to find out how much i resonated with the information regarding cannabis usage and the effect on our consciousness and attention-focus in (in between) the left and right hemisphere.
    Amongst other things of what i experienced, is the experience/feeling of being awake and asleep at the same time, like being conscious in the sub- or unconsciousness. Like with lucid dremaing where you “wake up” and become consciouss inside the dream.
    I also felt like being one with the now and with everything, and very aware/awake, and at total peace. It was a truly amazing experience.

    Thanks alot, Sebastián Marincolo for bringing this information to the net. It was very confirming and satisfying to me.

    1. Sebastian Marincolo

      Hi Ole, thanks your very interesting comment – here I am with a reply almost 8 years later 😉 I hope you still explore and enjoy a cannabis high along these lines!

  4. Cannabis is the most useful plant on the planet; food, clothing, shelter, energy, medicine, insight, re-creation. It has been mankinds companion and helpmate since the beginning. Any law against it is a crime against humanity, creation and the Creator.

  5. Men of the Earth have known the power of cannabis for centuries. Mr. Hearst made it part of the American Game and his rule was one of the more successful business/social manipulations of modern time. To bad they were never able to completely control, and in effect, set up the Legislation that is now sweeping the People of the States. The right to decide on cannabis is now a national issue. God Speed Free People of the World.

  6. Drs. Sagan and Grinspoon were men before their times. Cannabis does, indeed, open the mind to new ideas while somewhat blocking the ability of the mind to clutter thought with mundane matters.

    Taken to its limit, perhaps the lack of Cannabis in the daily regimen of U.S. leaders is why there is such a lack of positive leadership?

  7. Lovely. Such fond memories of Carl’s wonderful Cosmos series from childhood. I briefly discuss Carl’s use of the herb in a new book (Cannabis Regeneration) from Green Candy Press – forthcoming: Sept 2015. Carl was proof that you could explore both the inner-self and the universe with enthusiasm, vigour, passion, and an open mind.

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  • Author_profile-Sebastian-Marincolo

    Sebastian Marincolo

    Marincolo completed his doctorate with a focus on the philosophy of mind & neurocognition and has published many essays and four books on the mind-enhancing potential of the cannabis high. He also produced the macro photo art series “The Art of Cannabis”. He worked as a writer, blogger, photographer, photo artist, creative director, as well as a Director of Communications for one of the biggest cannabis companies in the world.
    More about this author
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