# The Library: Public-Domain Books Behind Operant Conditioning

> Full text of nine public-domain books behind the science of learning from consequences: Thorndike, Morgan, James, Yerkes, Pfungst, Romanes, Darwin. Free.

- Source: https://operantconditioning.com/library/
- Author: Ryan Martinson (https://operantconditioning.com/about/)
- Publisher: Operant Conditioning Inc.
- Published: 2026-09-12 · Updated: 2026-09-12
- Manifest: https://operantconditioning.com/library/library.json
- Agent index: https://operantconditioning.com/library/llms.txt
- License: this page https://operantconditioning.com/terms/#copyright; the books themselves are public domain (see each book)

---
*Library*

The public-domain books that operant conditioning was built from, as complete texts, free to read and published in formats that software and AI agents can use directly.

**In brief**

- 9 books, 1,288,625 words, 127 chapter files. All public domain in the United States; seven of the nine are public domain everywhere.
- Start with Thorndike's Chapter II and Chapter VI, then Morgan on trial and error and James on habit.
- For software: https://operantconditioning.com/library/library.json describes every book and chapter; each book has index.md, book.txt and a chapters/ folder.

## The books

- **[Animal Intelligence: Experimental Studies](https://operantconditioning.com/library/thorndike-animal-intelligence/)** — Edward L. Thorndike, 1911. The puzzle-box experiments and the law of effect: the direct ancestor of operant conditioning. 86,616 words, 8 sections, public domain worldwide. Markdown: https://operantconditioning.com/library/thorndike-animal-intelligence/index.md · Text: https://operantconditioning.com/library/thorndike-animal-intelligence/book.txt · Chapters: https://operantconditioning.com/library/thorndike-animal-intelligence/chapters/index.md
- **[Animal Behaviour](https://operantconditioning.com/library/morgan-animal-behaviour/)** — C. Lloyd Morgan, 1900. Morgan's account of learning by trial and error, instinct, and the limits of what animal behavior lets us infer. 115,874 words, 8 sections, public domain worldwide. Markdown: https://operantconditioning.com/library/morgan-animal-behaviour/index.md · Text: https://operantconditioning.com/library/morgan-animal-behaviour/book.txt · Chapters: https://operantconditioning.com/library/morgan-animal-behaviour/chapters/index.md
- **[The Principles of Psychology, Volume 1](https://operantconditioning.com/library/james-principles-of-psychology-vol-1/)** — William James, 1890. Volume 1 of James's masterwork, including the chapter on Habit that every account of behavior change still quotes. 237,258 words, 17 sections, public domain worldwide. Markdown: https://operantconditioning.com/library/james-principles-of-psychology-vol-1/index.md · Text: https://operantconditioning.com/library/james-principles-of-psychology-vol-1/book.txt · Chapters: https://operantconditioning.com/library/james-principles-of-psychology-vol-1/chapters/index.md
- **[The Principles of Psychology, Volume 2](https://operantconditioning.com/library/james-principles-of-psychology-vol-2/)** — William James, 1890. Volume 2: instinct, the emotions, and the will, including the ideo-motor theory of action. 231,048 words, 12 sections, public domain worldwide. Markdown: https://operantconditioning.com/library/james-principles-of-psychology-vol-2/index.md · Text: https://operantconditioning.com/library/james-principles-of-psychology-vol-2/book.txt · Chapters: https://operantconditioning.com/library/james-principles-of-psychology-vol-2/chapters/index.md
- **[The Dancing Mouse: A Study in Animal Behavior](https://operantconditioning.com/library/yerkes-the-dancing-mouse/)** — Robert M. Yerkes, 1907. A complete experimental study of one animal's learning: discrimination boxes, labyrinths, learning curves, and the efficiency of training methods. 82,710 words, 20 sections, public domain in the US. Markdown: https://operantconditioning.com/library/yerkes-the-dancing-mouse/index.md · Text: https://operantconditioning.com/library/yerkes-the-dancing-mouse/book.txt · Chapters: https://operantconditioning.com/library/yerkes-the-dancing-mouse/chapters/index.md
- **[Clever Hans (The Horse of Mr. von Osten): A Contribution to Experimental Animal and Human Psychology](https://operantconditioning.com/library/pfungst-clever-hans/)** — Oskar Pfungst, 1911. The horse that could not count: how Pfungst showed Hans was reading tiny movements of his questioners, and why blind procedures exist. 72,664 words, 14 sections, public domain in the US. Markdown: https://operantconditioning.com/library/pfungst-clever-hans/index.md · Text: https://operantconditioning.com/library/pfungst-clever-hans/book.txt · Chapters: https://operantconditioning.com/library/pfungst-clever-hans/chapters/index.md
- **[Animal Intelligence](https://operantconditioning.com/library/romanes-animal-intelligence/)** — George J. Romanes, 1882. The great anecdotal survey of animal minds that experimental psychology was invented to replace. 196,963 words, 20 sections, public domain worldwide. Markdown: https://operantconditioning.com/library/romanes-animal-intelligence/index.md · Text: https://operantconditioning.com/library/romanes-animal-intelligence/book.txt · Chapters: https://operantconditioning.com/library/romanes-animal-intelligence/chapters/index.md
- **[Animal Life and Intelligence](https://operantconditioning.com/library/morgan-animal-life-and-intelligence/)** — C. Lloyd Morgan, 1891. Morgan's first full treatment of animal minds, with his early chapters on habit, instinct and the senses. 165,549 words, 13 sections, public domain worldwide. Markdown: https://operantconditioning.com/library/morgan-animal-life-and-intelligence/index.md · Text: https://operantconditioning.com/library/morgan-animal-life-and-intelligence/book.txt · Chapters: https://operantconditioning.com/library/morgan-animal-life-and-intelligence/chapters/index.md
- **[The Expression of the Emotions in Man and Animals](https://operantconditioning.com/library/darwin-expression-of-the-emotions/)** — Charles Darwin, 1872. Darwin on habit: how serviceable actions become habitual, associated, and inherited. 99,943 words, 15 sections, public domain worldwide. Markdown: https://operantconditioning.com/library/darwin-expression-of-the-emotions/index.md · Text: https://operantconditioning.com/library/darwin-expression-of-the-emotions/book.txt · Chapters: https://operantconditioning.com/library/darwin-expression-of-the-emotions/chapters/index.md

## A reading order for operant conditioning

1. **Start with Thorndike.** Chapter II is the 1898 monograph: the puzzle boxes, the time-curves, and the case against anecdotes. Chapter VI states the law of effect and the law of exercise. Everything on this site descends from these two chapters. [Chapter II. Animal Intelligence; an Experimental Study of the Associative Processes in Animals](https://operantconditioning.com/library/thorndike-animal-intelligence/chapters/03-animal-intelligence-an-experimental-study-of-the.md) · [Chapter VI. Laws and Hypotheses for Behavior](https://operantconditioning.com/library/thorndike-animal-intelligence/chapters/07-laws-and-hypotheses-for-behavior.md)
2. **Then Morgan on trial and error.** Chapter IV of Animal Behaviour is the clearest pre-Thorndike account of learning from consequences, and the source of the rule of parsimony that keeps comparative psychology honest. [Chapter IV. Intelligent Behaviour](https://operantconditioning.com/library/morgan-animal-behaviour/chapters/05-intelligent-behaviour.md)
3. **James on habit.** Chapter IV of the Principles is the essay on habit that habit-formation writing still quotes, with the maxims at the end. Thorndike was in the audience. [Chapter IV. Habit](https://operantconditioning.com/library/james-principles-of-psychology-vol-1/chapters/05-habit.md)
4. **Yerkes on methods.** Chapters XII to XVI show what a complete experimental programme on one animal's learning looked like in 1907: discrimination boxes, labyrinths, learning curves, retention, and a comparison of training methods. [Chapter XII. Educability: Methods of Learning](https://operantconditioning.com/library/yerkes-the-dancing-mouse/chapters/14-educability-methods-of-learning.md) · [Chapter XIII. Habit Formation: the Labyrinth Habit](https://operantconditioning.com/library/yerkes-the-dancing-mouse/chapters/15-habit-formation-the-labyrinth-habit.md) · [Chapter XIV. Habit Formation: the Discrimination Method](https://operantconditioning.com/library/yerkes-the-dancing-mouse/chapters/16-habit-formation-the-discrimination-method.md) · [Chapter XV. The Efficiency of Training Methods](https://operantconditioning.com/library/yerkes-the-dancing-mouse/chapters/17-the-efficiency-of-training-methods.md) · [Chapter XVI. The Duration of Habits: Memory and Re-Learning](https://operantconditioning.com/library/yerkes-the-dancing-mouse/chapters/18-the-duration-of-habits-memory-and-re-learning.md)
5. **Pfungst on cues.** Chapter V explains how a horse answered arithmetic questions by reading the questioner's posture. It is the founding case of stimulus control by unnoticed cues, and of the experimenter effect. [Chapter V. Explanation of the Observations](https://operantconditioning.com/library/pfungst-clever-hans/chapters/07-explanation-of-the-observations.md)
6. **Background, in any order.** Darwin's first three chapters on serviceable associated habits; Romanes's introduction, to see what the experimenters were reacting against; Morgan's earlier chapters on habit and instinct; James's chapters on instinct and will in volume 2.

## For AI agents and software

- `https://operantconditioning.com/library/library.json` — every book: author, dates, edition, copyright status, word counts, why it matters, and the URL of every chapter file.
- `https://operantconditioning.com/library/llms.txt` — the catalogue as a short Markdown index.
- `https://operantconditioning.com/library/<book>/index.md` — the whole book as one Markdown file with a metadata header and table of contents.
- `https://operantconditioning.com/library/<book>/chapters/NN-slug.md` — one file per chapter, each with a header naming the book and the previous and next files; `chapters/index.md` lists them.
- `https://operantconditioning.com/library/<book>/book.txt` — plain text, footnotes marked [n].

Conventions: chapter headings are `##`, sections `###`/`####`; footnotes use `[^n]`, numbered continuously through each book; figures are `![caption](images/…)`; tables are Markdown tables or fenced text blocks. Budget roughly 1.3 tokens per word.

## What is not here, and why

None of B. F. Skinner's books is in the public domain; under the 95-year term, *The Behavior of Organisms* (1938) becomes free on 1 January 2034 and his later books follow year by year. The same applies to Hull, Tolman, Guthrie, Hebb and Ferster. Pavlov and Watson, and Thorndike's *Psychology of Learning*, are public domain in the United States and are next to be added:

- Ivan Pavlov, *Conditioned Reflexes* (1927). G. V. Anrep's translation (Oxford, 1927). Public domain in the United States; Pavlov died in 1936 and Anrep in 1955, so also public domain in life-plus-70 countries since 2026.
- Ivan Pavlov, *Lectures on Conditioned Reflexes* (1928). W. H. Gantt's translation (1928). Public domain in the United States; not yet in life-plus-70 countries (Gantt died in 1980).
- John B. Watson, *Behavior: An Introduction to Comparative Psychology* (1914). Public domain in the United States; in life-plus-70 countries not until 2029 (Watson died in 1958).
- John B. Watson, *Psychology from the Standpoint of a Behaviorist* (1919). Public domain in the United States; in life-plus-70 countries not until 2029.
- John B. Watson, *Behaviorism* (1924). Public domain in the United States; in life-plus-70 countries not until 2029.
- Edward L. Thorndike, *Educational Psychology, Vol. II: The Psychology of Learning* (1913). Public domain worldwide.

## Copyright, sources and reuse

Every book was published before 1931 and is public domain in the United States. In life-plus-70 countries seven of the nine are also public domain; the exceptions are Yerkes's *Dancing Mouse* (until 1 January 2027) and the English translation of *Clever Hans* (translator's dates unconfirmed). The texts are volunteer transcriptions distributed by Project Gutenberg (eBook numbers on each book's page) with the licence text, contents and indexes removed and the formatting converted to Markdown; the words are as transcribed. Project Gutenberg is a registered trademark of the Project Gutenberg Literary Archive Foundation, which is not affiliated with this site. Our editions add no rights of their own: copy, quote, mine, index, translate or republish freely.

## Frequently asked questions

**Are these the complete books?** Yes: every chapter, footnote and figure in the source transcription. Only tables of contents, lists of illustrations, indexes, advertisements and the Project Gutenberg licence were removed.

**Why is there nothing by Skinner?** His books are still under copyright; his first journal papers (1930–31) are only now entering the U.S. public domain, and *The Behavior of Organisms* follows in 2034.

**Can I use these texts to train or ground an AI model?** In the United States, yes. Elsewhere, the same for seven of the nine books; check the copyright note for Yerkes and Pfungst.

**I found a transcription error.** Email hello@operantconditioning.com with the book, chapter and sentence.