Hektoen International

A Journal of Medical Humanities

Scientific discoveries in dreams: Sleeping while the mind works

Edward Tabor
Bethesda, Maryland, United States

Some major scientific discoveries have been revealed in dreams during sleep. Since ancient times, Western culture has included a deep belief in the power of dreams to provide information. The Greek philosopher Heraclitus (c. 500 BC) spoke of how “even in their sleep men are at work.”1 The Roman emperor Marcus Aurelius (121 AD to 180 AD) noted that he learned about “remedies prescribed for me in dreams—especially in cases of blood-spitting and vertigo.”2 There are also some examples from more recent centuries.

August Kekulé (1829–1896), a German chemist, had been trying to figure out how groups of six carbon atoms could combine to make the organic chemicals that are found in all living beings. While doing so in 1865, he fell asleep in front of a fire and dreamed of a self-devouring snake chasing its tail, and when he awoke, he realized that the six carbon atoms must be joined together in a circle, now called the “benzene ring.”3

For many years, Kekulé’s dream has been well-known to students of chemistry, but it became even more widely known due to its use by the psychiatrist Carl Jung,3,4,5 although Jung described Kekulé’s dream being of the snake with its tail in its mouth. Jung used it as an example of symbols located in the “collective unconscious,” his concept of a library of subconscious images within the minds of all humans that he believed we inherited from our prehistoric ancestors.

Dmitri Mendeleev (1834–1907), a Russian chemist,6 wanted to design a table in which all of the sixty-three then-known chemical elements7 would be aligned based on their atomic weights. He had only been able to align about thirty elements until one night when he had a dream in which he saw almost all of the elements in a large tabular arrangement, a “periodic table.” The next morning, he wrote it down. In 2001, the historian of science Oliver Sacks examined Mendeleev’s drafts of the table and asserted that “Mendeleev did not wake from his dream with all the answers in place, but, more interestingly, perhaps, woke with a sense of revelation, so that within hours he was able to solve many of the questions that had occupied him for years.”6

Louis Agassiz (1807–1873), a prominent biologist at Harvard University, discovered the structure of a certain prehistoric fish by means of a recurring dream. In 1832, when he was twenty-five years old, he had been trying for two weeks to figure out what kind of fish had made a small fossilized impression on a stone slab. He awoke one night and realized that he had seen the fish in his sleep with all the missing features. He tried to hold onto the image in his mind, but it vanished. During the day, he continued to try to retrieve the image without success. The next night, he dreamed of the fish again, but with the same outcome when he awoke. On the third night, he put a paper and pencil next to his bed. As morning neared, the fish appeared again in a dream. Then, according to a posthumous biography written by his wife,8 “still half dreaming, in perfect darkness he traced these characters [of the fish] on the sheet of paper at the bedside.” In the morning, using the drawing as his guide, “he succeeded in chiseling away the surface of the stone under which portions of the fossilized fish proved to be hidden. When wholly exposed, it corresponded with his dream and his drawing, and he succeeded in classifying it with ease.”8

Otto Loewi (1873–1961), a German physiologist and pharmacologist, discovered in a dream how to show that chemicals transmit nerve messages across nerve junctions.9 In 1903, he had the idea that nerve transmission might occur by means of chemicals, but he could not then think of an experiment to show this. Seventeen years later, on two successive nights in 1920, he dreamed of a laboratory experiment that would allow him to verify his earlier hypothesis.9 On the first night, he awoke and wrote down the dream. In the morning, he was certain he had dreamed something important, but he could not remember it and could not decipher his writing. On the next night, he awoke at 3 a.m. and realized he had dreamed it again. By his own account, he “got up immediately, went to the laboratory, and performed a simple experiment on a frog heart according to the nocturnal design. … Its results became the foundation of the theory of chemical transmission of the nervous impulse.”9 For this discovery, he shared the Nobel Prize in Physiology or Medicine with Sir Henry Dale in 1936.

Loewi’s analysis of this experience provides some insight into how dreams can lead to scientific discoveries:

The story of this discovery shows that an idea may sleep for decades in the unconscious mind and then suddenly return. Further, it indicates that we should sometimes trust a sudden intuition without too much skepticism. If carefully considered in the daytime, I would undoubtedly have rejected the kind of experiment I performed. … It was good fortune that at the moment of the hunch I did not think but acted immediately.9  

To further complicate this experience, thirty-five years later, around 1955, he came across a paper he had written in 1918 using a similar experiment for a different purpose. He then concluded that the dream in 1920 represented the subconscious association of the hypothesis of 1903 with the method tested in 1918.

Srinivasa Ramanujan (1887–1920) was an Indian mathematical genius who went from poverty in southern India to work at Cambridge University in the United Kingdom and received the highest honors in world mathematics. He told a friend that the Hindu goddess Namagiri gave him mathematical insights in his dreams. He told another friend that in his dreams he saw drops of blood associated with the god Narasimha, the male consort of Namagiri, after which “scrolls containing the most complicated mathematics used to unfold before his eyes.”10 However, one of his biographers expressed doubts whether he really believed that his ideas came in dreams.10

Henri Poincaré (1854–1912), a prominent French mathematician, reported that solutions to mathematical problems often “come to me in the morning or evening in my bed while in a semi-hypnagogic state.”11 Hypnagogic sleep12 is a drowsy state that sometimes occurs during the transition from waking to sleep and often includes episodic dream-like visions. However, the visions of these states differ from actual dreams in having less emotional content. As in dreams, however, the working of subconscious ideas can be released from the inhibitions of consciousness during hypnagogic states. Poincaré said that these kinds of scientific inspirations came to him throughout his life with some regularity. He described one such occasion when “ideas arose in crowds; I sensed them colliding with each other, until two of them linked up together, as it were, to form a stable combination.” The next morning, he found that he had the solution to a problem with which he had been struggling for two weeks.11


Most scientific solutions do not arrive in dreams. Every year, thousands of important scientific problems are solved by thousands of scientists around the world, mostly as a result of dedicated sustained work and careful thinking. A few may result from sudden inspirations during waking hours, and even fewer from dreams.

Most of the dreams discussed here occurred to people who were thinking deeply about a specific problem during their waking hours. It is possible that such dreams may only occur in the context of intensive scientific thinking.

Nevertheless, solutions to scientific problems in dreams or in a hypnagogic state may occur more often than we realize. It is very difficult to remember any dreams even a few seconds after awaking, and scientific solutions might be found more often in dreams if more people remembered their dreams after awaking.

The subconscious mind is constantly at work, during waking and sleeping, linking different ideas that the dreamer has not seen connections between. The dream, if remembered on awaking, reveals those connections to the conscious mind. Carl Jung likened these dream revelations to the sudden flash of insight from the subconscious mind of a genius. He wrote that “the capacity of the human psyche to produce such new material is particularly significant when one is dealing with dream symbolism, for I have found again and again in my professional work that the images and ideas that dreams contain … [sometimes] express new thoughts that have never yet reached the threshold of consciousness.”5

Dreams, of course, no matter how insightful, are not a substitute for further research and experimental proof. Kekulé insisted it was important to verify the ideas revealed in dreams and that we should “beware of publishing our dreams before they have been examined by the conscious understanding.”11


  1. Heraclitus, quoted in Marcus Aurelius. Meditations. Translated by M. Staniforth. Penguin, New York, 2004, page 69, item 42.
  2. Marcus Aurelius. Meditations. Translated by M. Staniforth. Penguin, New York, 2004, page 10.
  3. Browne, MW. “The benzene ring: dream analysis.” The New York Times, August 16, 1988, page C10. Viewed at https://www.nytimes.com/1988/08/16/science/the-benzene-ring-dream-analysis.html.
  4. Jung, CG. The Psychology of Transference, Princeton University Press, 1969, pages 4-5. Viewed at The Internet Archive at https://archive.org/details/psychologyoftran00jung/page/n1/mode/2up.
  5. Jung, CG. “Approaching the unconscious,” in Jung, CG, von Franz, M-L, Henderson, JL, Jacobi, J, and Jaffé, A. Man and his Symbols, Doubleday, Garden City, NY, 1964 (posthumous), page 38.
  6. Sacks, O. Uncle Tungsten: Memories of a Chemical Boyhood. Vintage Books, New York, 2001, pages 198-199.
  7. Mazzarello, P. “What dreams may come?” Nature 2000; 408:523.
  8. Agassiz, ECC. Louis Agassiz: His Life and Correspondence. Cambridge, MA, 1885. Project Gutenberg eBook, 2020 update, eBook # 6078, pages 76-77. Viewed at https://www.gutenberg.org/cache/epub/6078/pg6078.html.
  9. Loewi, O. “An autobiographical sketch.” Perspectives in Biology and Medicine 1960;4:3-25.
  10. Kanigel, R. The Man Who Knew Infinity: A Life of the Genius Ramanujan. Washington Square Press, New York, 1991, pages 36, 98, 281.
  11. Rocke, AJ. “Kekulé’s ‘dreams’,” in Image and Reality: Kekulé, Kopp, and the Scientific Imagination. University of Chicago Press, Chicago, 2010, pages 293-323.
  12. Ghibellini R and Meier B. “The hypnagogic state: A brief update.” J. Sleep Res. 2023;32: e13719. Doi: 10.1111jsr.13719.

EDWARD TABOR, M.D. has worked at the US Food and Drug Administration, the National Cancer Institute (NIH), and Fresenius Kabi. He has published widely on viral hepatitis, liver cancer, and pharmaceutical regulatory affairs.

Fall 2023



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