Walter Pitts

Last updated 2026.03.24

{{short description|American logician and computational neuroscientist}} {{use mdy dates|date=December 2024}} {{Infobox scientist | name = Walter Pitts | birth_name = Walter Harry Pitts Jr. | image = 1954 Walter Pitts and a blackboard.jpg | image_size = | alt = | caption = Pitts around 1954 when he was at M.I.T. | birth_date = {{Birth date|1923|4|23}} | birth_place = [[Detroit]], [[Michigan]], U.S. | death_date = {{Death date and age|1969|5|14|1923|4|23}} | death_place = [[Cambridge]], [[Massachusetts]], U.S. | residence = | citizenship = | nationality = | fields = [[Logician]] | workplaces = | alma_mater = | doctoral_advisor = | academic_advisors = | doctoral_students = | notable_students = | known_for = * [[A Logical Calculus of the Ideas Immanent in Nervous Activity|A logical calculus of the ideas immanent in nervous activity]]

  • [[Artificial neural network]] | author_abbrev_bot = | author_abbrev_zoo = | influences = | influenced = | awards = | signature = | signature_alt = | footnotes = }} [[Image:Lettvin Pitts.jpg|thumb|Walter Pitts (right) with [[Jerome Lettvin]], co-author of the [[cognitive science]] paper "What the Frog's Eye Tells the Frog's Brain" (1959)]] '''Walter Harry Pitts Jr.''' (April 23, 1923 – May 14, 1969) was an American [[logician]] who worked in the field of [[computational neuroscience]].Smalheiser, Neil R. [http://muse.jhu.edu/login?uri=/journals/perspectives_in_biology_and_medicine/v043/43.2smalheiser.html "Walter Pitts"] {{Webarchive|url=https://web.archive.org/web/20160304001349/http://muse.jhu.edu/login?uri=%2Fjournals%2Fperspectives_in_biology_and_medicine%2Fv043%2F43.2smalheiser.html |date=2016-03-04 }}, ''Perspectives in Biology and Medicine'', Volume 43, Number 2, Winter 2000, pp. 217–226, The Johns Hopkins University Press He proposed landmark theoretical formulations of neural activity and generative processes that influenced diverse fields such as [[cognitive sciences]] and [[psychology]], [[philosophy]], [[neuroscience]]s, [[computer science]], [[artificial neural network]]s, [[cybernetic]]s and [[artificial intelligence]], together with what has come to be known as the [[generative science]]s. He is best remembered for having written, along with [[Warren Sturgis McCulloch]], a seminal paper in scientific history, titled ''[[A Logical Calculus of the Ideas Immanent in Nervous Activity|A Logical Calculus of Ideas Immanent in Nervous Activity]]'' (1943). This paper proposed the first mathematical model of a [[neural network]]. The unit of this model, a simple formalized neuron, is still the standard of reference in the field of neural networks. It is often called a [[McCulloch–Pitts neuron]]. Prior to that paper, he formalized his ideas regarding the fundamental steps to building a [[Turing machine]] in "The Bulletin of Mathematical Biophysics" in an essay titled "Some observations on the simple neuron circuit".

==Early life== Walter Pitts was born in [[Detroit]], [[Michigan]], on April 23, 1923, the son of Walter and Marie (née Welsia). An [[Autodidacticism|autodidact]], he taught himself [[logic]] and [[mathematics]] as a child and became a proficient reader in several languages, including [[Greek language|Greek]] and [[Latin]]. He is widely remembered for having spent three days in a library, at the age of 12, reading ''[[Principia Mathematica]]'' and sent a letter to [[Bertrand Russell]] pointing out what he considered serious problems with the first half of the first volume. Russell was appreciative and invited him to study at [[Cambridge University]] at age 12. The offer was not taken up; however, Pitts did decide to become a logician. At age 15 he left home to study.

==Academic career== Pitts probably continued to correspond with Bertrand Russell; and at the age of 15 he attended Russell's lectures at the [[University of Chicago]].Cf. Anderson (1998) [https://books.google.com/books?id=-l-yim2lNRUC&q=walter+pitts p.218] conversation with [[Michael A. Arbib]] He stayed there, without registering as a student. While there, in 1938 he met [[Jerome Lettvin]], a [[pre-medical]] student, and the two became close friends.Cf. Conway, Flo; Siegelman, Jim (2005), [https://books.google.com/books?id=gwaDvnqU6yYC&q=pitts p.138] Russell was a visiting professor at the University of Chicago in the fall of 1938, and he directed Pitts to study with the logician [[Rudolf Carnap]]. Pitts met Carnap at Chicago by walking into his office during office hours, and presenting him with an annotated version of Carnap's recent book on logic, ''The Logical Syntax of Language''.Singer, Milton, "A Tale of Two Amateurs Who Crossed Cultural Frontiers with Boole's Symbolical Algebra", Semiotica. Volume 105, Issue 1-2, 1995. Cf. [http://www.reference-global.com/doi/abs/10.1515/semi.1995.105.1-2.134 pp. 134–138]{{Dead link|date=February 2020 |bot=InternetArchiveBot |fix-attempted=yes }} Since Pitts did not introduce himself, Carnap spent months searching for him, and, when he found him, he obtained for him a menial job at the university and had Pitts study with him. Pitts at the time was homeless and without income.[http://cognet.mit.edu/MITECS/Entry/lettvin1 "Pitts, Walter"], MIT Encyclopedia of [[Cognitive Science]] ({{webarchive |url=https://web.archive.org/web/20030830083757/http://cognet.mit.edu/MITECS/Entry/lettvin1.html |date=August 30, 2003 }}) He mastered Carnap's abstract logic, then met with and was intrigued by the work of the Ukrainian mathematical physicist [[Nicolas Rashevsky]], who was also at Chicago and was the founder of [[Biophysics|mathematical biophysics]], remodeling biology on the structure of the physical sciences and [[mathematical logic]].Cf. Conway, Flo; Siegelman, Jim (2005), [https://books.google.com/books?id=gwaDvnqU6yYC&q=pitts p.139] Pitts also worked closely with the mathematician [[Alston Scott Householder]], who was a member of Rashevsky's group.Cf. Aizawa & SchlatterCf. Anderson (1998) [https://books.google.com/books?id=-l-yim2lNRUC&q=alston+householder p.105] conversation with [[Jack D. Cowan]]Cf. Aizawa 1992 During his studies under Carnap, Pitts was also a regular attendant at Nicolas Rashevsky’s seminars in theoretical biology, which included Frank Offner, Herbert Landahl, Alston Householder, and the neuroanatomist Gerhardt von Bonin from the [[University of Illinois at Chicago]]. In 1940, Von Bonin introduced Lettvin to [[Warren McCulloch]], who would become a professor of psychiatry at Illinois.

In 1941 [[Warren McCulloch]] took a position as professor of psychiatry at the [[University of Illinois at Chicago]], and in early 1942 he invited Pitts, who was still homeless, together with Lettvin to live with his family.{{cite journal |last1=Smalheiser|first1=Neil |title=Walter Pitts |journal=Perspectives in Biology and Medicine|date=2000 |volume=43 |issue=43,2 |pages= 217–226|doi=10.1353/pbm.2000.0009 |pmid=10804586 |s2cid=8757655 }} In the evenings, McCulloch and Pitts collaborated. Pitts was familiar with the work of [[Gottfried Leibniz]] on computing and they considered the question of whether the nervous system could be considered a kind of universal computing device as described by Leibniz. This led to their seminal [[neural network]]s paper "A Logical Calculus of Ideas Immanent in Nervous Activity". After five years of unofficial studies, the University of Chicago awarded Pitts an [[Associate of Arts]] (his only earned degree) for his work on the paper.{{cite book|url=https://books.google.com/books?id=4pjlAgAAQBAJ&q=%22Research+Laboratory+of+Electronics%22+%22walter+pitts%22&pg=PA157|title=Kurt Gödel: Collected Works|first=Kurt|last=Gödel|date=9 January 2014|publisher=Clarendon Press|via=Google Books|isbn=9780191003776}}

In 1943, Lettvin introduced Pitts to [[Norbert Wiener]] at the [[Massachusetts Institute of Technology]]. Their first meeting, where they discussed Wiener's proof of the [[ergodic theory|ergodic theorem]], went so well that Pitts moved to [[Greater Boston]] to work with Wiener. While Pitts was an unofficial student under the aegis of Wiener at MIT until their acrimonious parting in 1952, he formally enrolled as a graduate student in the [[physics]] department during the 1943–1944 academic year and in the [[electrical engineering]] department from 1956–1958.Cf. Conway, Flo; Siegelman, Jim (2005), [https://books.google.com/books?id=gwaDvnqU6yYC&q=pitts pp. 141–2]

In 1944, Pitts was hired by [[Kellex Corporation]] (later acquired in 1950 by [[Vitro Corporation]]) in New York City, part of the [[Manhattan Project|Atomic Energy Project]].Cf. Anderson (1998) [https://books.google.com/books?id=-l-yim2lNRUC&q=walter+pitts p.4] conversation with Jerome Y. Lettvin

From 1946, Pitts was a core member of the [[Macy conferences]], whose principal purpose was to set the foundations for a general science of the workings of the human mind.

==Personal life and death== In 1951, Wiener convinced [[Jerome Wiesner]] to hire some physiologists of the nervous system. A group was established with Pitts, Lettvin, McCulloch, and [[Patrick David Wall|Pat Wall]]. Pitts wrote a large dissertation on the properties of neural nets connected in three dimensions. Lettvin described him as "in no uncertain sense the genius of the group ... when you asked him a question, you would get back a whole textbook."{{Cite book |last=Anderson |first=James A. |url=http://archive.org/details/talkingnetsoralh00ande |title=Talking nets : an oral history of neural networks |last2=Rosenfeld |first2=Edward |date=1998 |publisher=Cambridge, Mass. : MIT Press |others=Internet Archive |isbn=978-0-262-01167-9}} Pitts never married. Pitts was also described as an eccentric, refusing to allow his name to be made publicly available. He continued to refuse all offers of advanced degrees or positions of authority at MIT, in part as he would have to sign his name.

In 1952, Wiener suddenly turned against McCulloch—his wife, Margaret Wiener, hated McCulloch{{cite magazine | last = Gefter | first = Amanda | date = February 5, 2016

| title = The Man Who Tried to Redeem the World with Logic | url = https://nautil.us/the-man-who-tried-to-redeem-the-world-with-logic-rp-235254/ | magazine = Nautilus | publisher = MIT Press and NautilusThink | publication-date = February 5, 2017

| issue = 21 | issn = 2372-1758 | archive-url = https://web.archive.org/web/20160614095134/http://nautil.us/issue/21/information/the-man-who-tried-to-redeem-the-world-with-logic | archive-date= June 14, 2016 | access-date = 13 Jul 2016 | quote = There was just one person who wasn’t happy about the reunion: Wiener's wife. Margaret Wiener was, by all accounts, a controlling, conservative prude—and she despised McCulloch's influence on her husband. McCulloch hosted wild get-togethers at his family farm in Old Lyme, Connecticut, where ideas roamed free and everyone went skinny-dipping. It had been one thing when McCulloch was in Chicago, but now he was coming to Cambridge and Margaret wouldn’t have it. And so she invented a story. She sat Wiener down and informed him that when their daughter, Barbara, had stayed at McCulloch's house in Chicago, several of "his boys" had seduced her. Wiener immediately sent an angry telegram to Wiesner: "Please inform [Pitts and Lettvin] that all connection between me and your projects is permanently abolished. They are your problem. Wiener." He never spoke to Pitts again. }}—and broke off relations with anyone connected to him, including Pitts.

Although he remained employed as a [[research associate]] in the Research Laboratory of Electronics at MIT "as little more than a technicality"{{cite web|url=http://nautil.us/issue/21/information/the-man-who-tried-to-redeem-the-world-with-logic|title=The Man Who Tried to Redeem the World with Logic|first=Amanda|last=Gefter|date=5 February 2015|website=Nautilus}} for the rest of his life, Pitts became increasingly [[Social isolation|socially isolated]]. In 1959, the paradigmatic "What the Frog’s Eye Tells the Frog’s Brain" (credited to [[Humberto Maturana]], Lettvin, McCulloch and Pitts) conclusively demonstrated that "analog processes in the eye were doing at least part of the interpretive work" in image processing as opposed to "the brain computing information digital neuron by digital neuron using the exacting implement of mathematical logic", leading Pitts to burn his unpublished doctoral dissertation on probabilistic three-dimensional neural networks and years of unpublished research. He took little further interest in work, excepting only a collaboration with Lettvin and Robert Gesteland which produced a paper on [[olfaction]] in 1965.

Pitts died in 1969 of bleeding [[esophageal varices]], a condition usually associated with [[cirrhosis]] and [[alcoholism]].

==Publications==

  • Walter Pitts, [https://doi.org/10.1007%2FBF02477942 "Some observations on the simple neuron circuit"], ''[[Bulletin of Mathematical Biology]]'', Volume 4, Number 3, 121–129, 1942.
  • [[Warren McCulloch]] and Walter Pitts, "A Logical Calculus of Ideas Immanent in Nervous Activity", 1943, ''[[Bulletin of Mathematical Biophysics]]'' 5:115–133. Reprinted in ''Neurocomputing: Foundations of Research''. Edited by [[James A. Anderson (cognitive scientist)|James A. Anderson]] and Edward Rosenfeld. MIT Press, 1988. [http://dl.acm.org/citation.cfm?id=104377 pages 15–27]
  • Warren McCulloch and Walter Pitts, "On how we know universals: The perception of auditory and visual forms", 1947, ''Bulletin of Mathematical Biophysics'' 9:127–147.
  • R. Howland, Jerome Lettvin, Warren McCulloch, Walter Pitts, and P. D. Wall, "Reflex inhibition by dorsal root interaction", 1955, ''Journal of Neurophysiology'' 18:1–17.
  • P. D. Wall, Warren McCulloch, Jerome Lettvin and Walter Pitts, "Effects of strychnine with special reference to spinal afferent fibres", 1955, ''Epilepsia Series'' 3, 4:29–40.
  • Jerome Lettvin, [[Humberto Maturana]], Warren McCulloch, and Walter Pitts, "What the Frog's Eye Tells the Frog's Brain", 1959, ''Proceedings of the Institute of Radio Engineers'' 47: 1940–1951.
  • Humberto Maturana, Jerome Lettvin, Warren McCulloch, and Walter Pitts, "Anatomy and physiology of vision in the frog", 1960, ''Journal of General Physiology'', 43:129—175.
  • Robert Gesteland, Jerome Lettvin and Walter Pitts, "Chemical Transmission in the Nose of the Frog", 1965, ''J.Physiol''. 181, 525–529.

==References== {{reflist}}

==Further reading==

  • Aizawa, Kenneth, "Connectionism and artificial intelligence: history and philosophical interpretation", ''[[Journal of Experimental and Theoretical Artificial Intelligence]]'', Volume 4, Issue 4, 1992, pages 295–313
  • Aizawa, Kenneth; Schlatter, Mark, [https://doi.org/10.1007%2Fs11229-007-9182-9 "Walter Pitts and 'A Logical Calculus'"], ''Synthese'' (2008) 162:235–250.
  • Aizawa, Kenneth; Schlatter, Mark, [http://philpapers.org/rec/AIZALA "Another Look at McCulloch and Pitts's 'Logical Calculus'"] {{Webarchive|url=https://web.archive.org/web/20161108050705/http://philpapers.org/rec/AIZALA |date=November 8, 2016 }}, [[Centenary College of Louisiana]], [[Shreveport, Louisiana]]
  • Anderson, James A.; Rosenfeld, Edward (editors), [https://books.google.com/books?id=-l-yim2lNRUC ''Talking Nets: An Oral History of Neural Networks''], 1998. The interview with Jerome Lettvin discusses Walter Pitts.
  • Conway, Flo; Siegelman, Jim, [https://books.google.com/books?id=gwaDvnqU6yYC ''Dark hero of the information age: in search of Norbert Wiener, the father of Cybernetics''], Basic Books, 2005. Cf. [https://books.google.com/books?id=gwaDvnqU6yYC&q=walter+pitts p.138] & various.
  • Easterling, Keller, [http://www.cabinetmagazine.org/issues/5/walterpitts.php "Walter Pitts"], ''[[Cabinet (magazine)|Cabinet]]'', Issue 5 Winter 2001/02
  • [[Gualtiero Piccinini|Piccinini, Gualtiero]], [http://www.umsl.edu/~piccininig/First_Computational_Theory_of_Mind_and_Brain.pdf "The First Computational Theory of Mind and Brain: A Close Look at McCulloch and Pitts's 'Logical Calculus of Ideas Immanent in Nervous Activity'"]{{Dead link|date=July 2025 |bot=InternetArchiveBot |fix-attempted=yes }}, ''Synthese'' 141: 175–215, 2004.
  • A. Gefter, [https://nautil.us/the-man-who-tried-to-redeem-the-world-with-logic-rp-235254/ “The Man Who Tried to Redeem the World with Logic,”] The Best American Science and Nature Writing, 2016

== External links == {{Wikiquote}}

  • [https://nautil.us/the-man-who-tried-to-redeem-the-world-with-logic-rp-235254/ "The Man who Tried to Redeem the World with Logic"], ''Nautilus Magazine'' issue 21, 5 February 2015

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{{DEFAULTSORT:Pitts, Walter}} [[Category:1923 births]] [[Category:1969 deaths]] [[Category:20th-century American mathematicians]] [[Category:20th-century American psychologists]] [[Category:American cognitive neuroscientists]] [[Category:American logicians]] [[Category:Computational neuroscientists]] [[Category:Massachusetts Institute of Technology alumni]] [[Category:Philosophers from Michigan]] [[Category:University of Chicago alumni]]