Expectancy and conditioning in placebo analgesia: Separate or connected processes?
Bibliographic record
Abstract
Expectancy and conditioning are often tested as opposing explanations of placebo analgesia, most commonly by pitting the effects of a conditioning procedure against those of a verbally-induced expectation for pain reduction. However, conditioning procedures can also alter expectations, such that the effect of conditioning on pain might be mediated by expectancy. We assessed the effect of conditioning on expected pain and placebo-induced pain reduction. Participants were told that the treatment (real or sham acupuncture) would affect one side of the arm but not the other. Because a real acupuncture effect would not be specific to a randomly selected side of the arm, any difference in pain between the "treated" and the "untreated" side would be a placebo effect. There were no significant main effects or interactions associated with type of acupuncture (real versus sham). In both groups, conditioning decreased expected pain for "treated" location and also increased the placebo effect (i.e., the difference in pain report between "treated" and "untreated" locations). In addition, mediation analysis lent support to the hypothesis that the effects of conditioning on placebo analgesia may be mediated by expectancy, although the size of this indirect effect requires further study.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.010 | 0.028 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.002 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.010 |
| Scholarly communication | 0.004 | 0.013 |
| Open science | 0.002 | 0.003 |
| Research integrity | 0.004 | 0.005 |
| Insufficient payload (model declined to judge) | 0.015 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".