Pavlovian conditioning 1927
A neutral signal repeatedly paired with a stimulus that already triggers a reflex begins to trigger a similar response by itself.
Main paper: Pavlov, I. P. (1927). Conditioned reflexes: An investigation of the physiological activity of the cerebral cortex (g. V. anrep, trans.). Oxford University Press. https://psychclassics.yorku.ca/Pavlov/lecture2.htm
The question
Can a signal that initially means nothing to an animal come to produce a reflex response through repeated pairing?
Design: paradigm
A general procedure used across many studies, laboratories and species, not one dated trial.
A procedure worked out and repeated in Pavlov's laboratory and later adopted widely. There is no single founding trial.
Before
- Tone alone
- Food alone
Result reportedTone: no salivation. Food: salivation
Pairing
- Tone, then food
- Repeated many times
Result reportedSalivation to food
After
- Tone alone
Result reportedSalivation to the tone
Original diagram drawn for this site from the descriptions in the sources. It is a simplified summary, not a figure from the paper.
Procedure
Pavlov was a physiologist studying digestion in dogs. His laboratory found that salivation could be triggered by signals that had come to predict food. The basic procedure pairs a neutral stimulus, such as the metronome sound described in his lectures, with food. The food reliably causes salivation. After repeated pairings the tone alone begins to cause salivation.
Vocabulary from this work is still used: the food is the unconditioned stimulus, the salivation to it is the unconditioned response, and the tone, once it works alone, is the conditioned stimulus, with the conditioned response it evokes.
Findings
Across dogs and sessions, signals paired with food acquired the power to evoke salivation. Presenting the signal repeatedly without food weakened the response, which later researchers call extinction. Related signals could also evoke responses, which is now called generalization.
This profile describes the paradigm in general terms and gives no sample sizes or trial counts, because it is not a report of one dated experiment.
Interpretation
Pavlov treated the result as a window on how the nervous system links events. Later accounts emphasize that the signal predicts the stimulus, not only that two events occur together.
Limits on what it shows
- Treating 'Pavlov's dogs' as one experiment hides that this is a family of procedures across many animals and variations.
- Textbook summaries simplify. Stimuli, equipment and timing varied across studies, and the common retelling with a bell is not verified here.
- Dog salivation does not by itself show how people learn fears, tastes or habits. Human studies are needed for that.
Ethics
Dogs underwent surgery so that salivary flow could be measured. Current animal research is reviewed for welfare and requires justification of the procedures, and many readers find these surgeries hard to accept.
Replication and reassessment
The familiar sound-and-food example compresses a research program into a few steps. Pavlov varied signals and procedures. Extinction and generalization also need explanation; acquiring a response does not mean that it will persist unchanged in every context.
Think it through. An original practice question written for this site.
A phone buzzes just before a friend usually shows you a funny video. After many repetitions you smile at the buzz alone. Which part plays the role of the conditioned stimulus, and what would extinction look like?
Show a way to reason about it
The buzz is the conditioned stimulus, because it was neutral and now predicts the video. Extinction would be the smile fading after many buzzes with no video. This is an invented example for practice, not a reported finding.
Nothing you think or select here is recorded.
Textbook connection
Covered in this sectionOpenStax Psychology 2e, 6.2 Classical Conditioning
Section covers Pavlov's dog procedure and the conditioning vocabulary.
Sources and access scope
Each label says how much of the source was opened while preparing this profile. An unopened source is listed so the claim can be checked, not because it was read.
- Pavlov, I. P. (1927). Conditioned reflexes: An investigation of the physiological activity of the cerebral cortex (g. V. anrep, trans.). Oxford University Press. https://psychclassics.yorku.ca/Pavlov/lecture2.htmOriginal researchSelected full-text sections inspected
Selected preparation and demonstration passages inspected. The sound described here is a metronome; this profile summarizes a general procedure, not one trial.
- Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020). Psychology 2e. OpenStax. https://openstax.org/books/psychology-2e/pages/6-2-classical-conditioningTextbook contextSelected textbook passages inspected
Textbook context. The tone and meat powder description follows this section's account of Pavlov's dogs.