Partial reinforcement, extinction, and placebo analgesia
Open accessAbstract
Numerous studies indicate that placebo analgesia can be established via conditioning procedures. However, these studies have exclusively involved conditioning under continuous reinforcement. Thus, it is currently unknown whether placebo analgesia can be established under partial reinforcement and how durable any such effect would be. We tested this possibility using electrocutaneous pain in healthy volunteers. Sixty undergraduates received placebo treatment (activation of a sham electrode) under the guise of an analgesic trial. The participants were randomly allocated to different conditioning schedules, namely continuous reinforcement (CRF), partial reinforcement (PRF), or control (no conditioning). Conditioning was achieved by surreptitiously reducing pain intensity during training when the placebo was activated compared with when it was inactive. For the CRF group, the placebo was always followed by a surreptitious reduction in pain during training. For the PRF group, the placebo was followed by a reduction in pain stimulation on 62.5% of trials only. In the test phase, pain stimulation was equivalent across placebo and no placebo trials. Both CRF and PRF produced placebo analgesia, with the magnitude of initial analgesia being larger after CRF. However, although the placebo analgesia established under CRF extinguished during test phase, the placebo analgesia established under PRF did not. These findings indicate that PRF can induce placebo analgesia and that these effects are more resistant to extinction than those established via CRF. PRF may therefore reflect a novel way of enhancing clinical outcomes via the placebo effect.
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Because expectations of low pain are more easily extinguished and more sensitive to sensory evidence, the positive PE condition was more vulnerable to an unmeasured variable than the negative PE condition.
“It is plausible that because expectations of low pain are more easily extinguished and more sensitive to sensory evidence18–21, the corresponding positive PE condition was more vulnerable to an unmeasured variable than the negative PE condition.”
From Boundary effects of expectation in human pain perception (2019) · cites this paper as [18]
The Discussion reports that placebo analgesia extinguished after continuous reinforcement but appeared resistant to extinction after partial reinforcement. It does not compare expectations of low versus high pain, measure those expectations, or establish that low-pain expectations are more sensitive to sensory evidence. The proposed vulnerability of the positive PE condition is the citing authors’ own inference. (LLM, conf=0.82)
Experimental — accuracy not yet measuredNocebo responses are less sensitive to sensory evidence than placebo responses.
“Nocebo responses are stronger, more difficult to extinguish and less sensitive to sensory evidence than placebo responses8,18–20.”
From Boundary effects of expectation in human pain perception (2019) · cites this paper as [18]
The Results (Test Phase; page unavailable) describe extinction of placebo analgesia, but do not compare placebo and nocebo responses. Searches for nocebo responses and sensory evidence found no passage assessing whether nocebo responses are less sensitive to sensory evidence. (LLM, conf=0.76)
Experimental — accuracy not yet measuredNocebo responses are more difficult to extinguish than placebo responses.
“Nocebo responses are stronger, more difficult to extinguish and less sensitive to sensory evidence than placebo responses8,18–20.”
From Boundary effects of expectation in human pain perception (2019) · cites this paper as [18]
The Discussion (page unavailable) describes extinction of placebo analgesia under continuous reinforcement, but does not compare it with extinction of nocebo responses. Searches for nocebo extinction and a placebo–nocebo comparison found no passage addressing the claimed difference. (LLM, conf=0.75)
Experimental — accuracy not yet measuredNocebo responses are stronger than placebo responses.
“Nocebo responses are stronger, more difficult to extinguish and less sensitive to sensory evidence than placebo responses8,18–20.”
From Boundary effects of expectation in human pain perception (2019) · cites this paper as [18]
The Results compare placebo analgesia under different reinforcement schedules, not the strength of nocebo versus placebo responses. Searches for nocebo and for a comparison of response magnitude found no such finding in our copy; nocebo appears in the References, but those entries do not establish the claim. (LLM, conf=0.78)
Experimental — accuracy not yet measuredPlacebo effects persisted over time when established throughout partial reinforcement, but not after continuous reinforcement.
“A different trend has been observed for positive partial reinforcement in which placebo effects persisted over time when established throughout partial reinforcement, but not after continuous reinforcement.5”
From Nocebo and pain: an overview of the psychoneurobiological mechanisms (2017) · cites this paper as [5]
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References 44 · Cited by 92
Research works printed but not linked: 1
- [1]Ader R White L Tursky B Schwartz GE 1985 Conditioned immunopharmacological effects in animals: Implications for a conditioning model of pharmacotherapy Placebo: Theory, research, and mechanisms New York Guilford Press 306 323
- Authors
- Au Yeung, S. T., Colagiuri, B., Lovibond, P. F., & Colloca, L.
- Affiliations
- The University of Sydney (AU)
- UNSW Sydney (AU)
- National Institutes of Health (US)
- Corresponding author
- Colagiuri, Ben
- Venue
- Pain
- Published
- 2014-06
- Volume
- 155
- Issue
- 6
- Pages
- 1110-1117
- ISSN
- 0304-3959 (ISSN-L)
- PMC
- PMC4025912
- OpenAlex
- W1992384900
- Cited by
- 92
- References
- 44
- Citations by year
- 2026: 3 · 2025: 2 · 2024: 9 · 2023: 13 · 2022: 2 · 2021: 6 · 2020: 13 · 2019: 7 · 2018: 12 · 2017: 11 · 2016: 4 · 2015: 10
- FWCI
- 4.65
- Type
- journal article
- Language
- en
- Open access
- green
- www.ncbi.nlm.nih.gov
- Locations
- Pain (publishedVersion)
- PubMed (publishedVersion)
- Europe PMC (PubMed Central) (acceptedVersion)
- PubMed Central (acceptedVersion)
- UNSWorks (UNSW Sydney) (submittedVersion, cc-by-nc-nd)
- UNSWorks (University of New South Wales, Sydney, Australia) (submittedVersion, cc-by-nc-nd)
- Funders
- National Institutes of Health (Z99 AT999999)
- Topics
- Life Sciences › Neuroscience › Cognitive Neuroscience › Pain Management and Placebo Effect
- Health Sciences › Medicine › Physiology › Pain Mechanisms and Treatments
- Life Sciences › Neuroscience › Cognitive Neuroscience › Memory and Neural Mechanisms
- Keywords
- placebo analgesia, partial reinforcement, extinction, electrocutaneous pain, conditioned pain modulation, continuous reinforcement, pain conditioning, placebo effect
- MeSH terms
- Adolescent, Analgesia, Transcutaneous Electric Nerve Stimulation, Extinction, Psychological, Female, Humans, Male, Pain Measurement, Reinforcement, Psychology, Placebo Effect, Young Adult
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