Thorndike's law of effect and its inconsistent description over the years
Thorndike's law of effect states that responses followed by satisfying consequences are strengthened; this review traces how later textbooks distorted his original 1911 formulation over the years.
01Research in Context
What this study did
Domjan read every major textbook and paper that quotes Thorndike’s law of effect.
He compared each quote to Thorndike’s 1905 and 1911 originals.
The goal: see how the wording changed over 100 years.
What they found
Most modern sources get the law wrong.
They drop Thorndike’s key phrase about ‘satisfyingness’ and add words he never used.
The errors appear in intro courses, grad texts, and even ABA blogs.
How this fits with other research
Weiss et al. (2001) shows another myth: ‘rewards kill motivation.’ Both papers warn that sloppy teaching spreads false facts.
Wolfe et al. (2023) gives a free tool to check if single-case data really replicate. Domjan gives a free history check: read the original before you teach.
Bernardy et al. (2023) describe how one scholar’s ideas can shape a whole grad program. Domjan shows how one mis-quote can shape a whole field.
Why it matters
If you teach, supervise, or write training materials, you are a gatekeeper. One wrong slide can echo for years. Pull Thorndike’s original paragraph, paste it next to your slide, and fix any mismatch before your next lecture.
What the law of effect states
Edward Thorndike introduced the law of effect in his 1911 book. In its original form, responses that are followed by a satisfying state of affairs are more likely to recur, while those followed by an annoying state become less likely.
Thorndike later softened the symmetrical half, concluding that reward strengthens connections far more reliably than punishment weakens them. The law became a cornerstone of instrumental and operant conditioning.
How it has been misdescribed
The review traces how many textbook statements of the law drift from Thorndike's own wording. Common distortions overstate the weakening effect of annoyers or recast the law in purely modern reinforcement terms.
The law of effect still matters for current debates about habitual versus goal-directed behavior, so the authors argue for describing it accurately rather than repeating inherited errors.
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Open your Thorndike slide, search ‘Thorndike 1911 law of effect pdf’, and delete any words he never wrote.
02At a glance
03Original abstract
The law of effect, originally proposed by E. L. Thorndike in a book that was published in 1911, had a major influence on the development of studies of instrumental or operant conditioning in the twentieth century. It remains a core concept in psychology and is invariably covered in undergraduate and graduate courses. Thorndike's law of effect also remains a topic of inquiry in contemporary efforts to understand the nature of habitual responses as contrasted with goal‐directed behavior. The mechanisms of the law of effect continue to be studied by behavioral and social psychologists as well as neuroscientists. However, many statements of the law of effect deviate in significant ways from Thorndike's original formulation. The present article reviews the history of Thorndike's law of effect and traces how the law has been, and continues to be, misrepresented. The hope is that familiarity with common misrepresentations of the law of effect will encourage greater consistency and clarity in discussions of the law and better appreciation of its role in contemporary research.
Journal of the Experimental Analysis of Behavior, 2026 · doi:10.1002/jeab.70073