In search of conditioned pain: an experimental analysis
Two pages on PainSci cite Kang 2023: 1. Chronic Pain as a Conditioned Behaviour 2. Can pain be conditioned? The plausibility and the evidence
PainSci commentary on Kang 2023: ?This page is one of thousands in the PainScience.com bibliography. It is not a general article: it is focused on a single scientific paper, and it may provide only just enough context for the summary to make sense. Links to other papers and more general information are provided wherever possible.
This paper presents a trio of related experiments to test the hypothesis that pain can undergo classical conditioning. In preparation for the experiment, participants were trained in a simulated setting to anticipate pain when touched on the hand with a blue pen, but not when touched with a yellow pen (“acquisition”). In the first test, the shock was happened when the pen touched a specific point on the hand; in the second, it was when the pen seemed to touch the hand in the virtual world; and in the third, the participants were told the pen could cause pain instead of just signaling it. This process definitely taught subjects to expect pain when they saw the blue pen, but only the second and third tests showed “some evidence” of actually feeling pain when a shock was not delivered. The results suggest that it’s possible for people to learn to feel pain from certain cues, but it might be quite rare or only happen in certain conditions.
original abstract †Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.
There is an ongoing debate about whether pain can be classically conditioned, but surprisingly, evidence is scarce. Here, we report 3 experiments investigating this idea. In a virtual reality task, healthy participants were approached and touched near or on their hand with a coloured pen (blue or yellow). During acquisition, participants learned that one of the colours of the pen (CS+) was predictive of a painful electrocutaneous stimulus (ECS) whereas the other coloured pen (CS-) was not. During the test phase, more frequent reports of experiencing an US when none was delivered ("false alarm") for the CS+ vs CS- qualified as evidence of conditioned pain. Notable differences between experiments were that the US was delivered when the pen touched a spot between the thumb and index finger (experiment 1; n = 23), when it virtually touched the hand (experiment 2; n = 28) and when participants were informed that the pen caused pain rather than simply predicting something (experiment 3; n = 21). The conditioning procedure proved successful in all 3 experiments: Self-reported fear, attention, pain, fear, and US expectancy were higher ( P < 0.0005) for the CS+ than the CS-. There was no evidence for conditioned pain in experiment 1, but there was some evidence in experiments 2 and 3. Our findings indicate that conditioned pain may exist, albeit most likely in rare cases or under specific situations. More research is needed to understand the specific conditions under which conditioned pain exists and the underlying processes (eg, response bias).
related content
- “New developments in the understanding and management of persistent pain,” Flor, Curr Opin Psychiatry, 2012.
- “Do clinicians think that pain can be a classically conditioned response to a non-noxious stimulus?,” Madden et al, Manual Therapy, 2016.
- “Can Pain or Hyperalgesia Be a Classically Conditioned Response in Humans? A Systematic Review and Meta-Analysis,” Madden et al, Pain Med, 2016.
Specifically regarding Kang 2023:
- “"Conditioned pain" remains unproven and unlikely (comment on Kang et al. PAIN 2023; 164: 2596-2605),” Cohen et al, Pain, 2024.
This page is part of the PainScience BIBLIOGRAPHY, which contains plain language summaries of thousands of scientific papers & others sources. It’s like a highly specialized blog. A few highlights:
- Classical Conditioning Fails to Elicit Allodynia in an Experimental Study with Healthy Humans. Madden 2017 Pain Med.
- Topical glyceryl trinitrate (GTN) and eccentric exercises in the treatment of mid-portion achilles tendinopathy (the NEAT trial): a randomised double-blind placebo-controlled trial. Kirwan 2024 Br J Sports Med.
- Placebo analgesia in physical and psychological interventions: Systematic review and meta-analysis of three-armed trials. Hohenschurz-Schmidt 2024 Eur J Pain.
- Recovery trajectories in common musculoskeletal complaints by diagnosis contra prognostic phenotypes. Aasdahl 2021 BMC Musculoskelet Disord.
- Cannabidiol (CBD) products for pain: ineffective, expensive, and with potential harms. Moore 2023 J Pain.