N-of-few Study of Pain Perception

Study Overview
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Brief Summary
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A behavioral study that will examine how pain perception is affected by different types of conditioning and by context, with a few participants and multiple sessions (N-of-few design).

Official Title
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Common and Distinct Mechanisms of Expectancy Effects Across Outcomes

Conditions
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Healthy

Intervention / Treatment
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* Behavioral: Symbolic conditioning
* Behavioral: Conditioning
* Behavioral: Instructions
* Behavioral: Counterfactual


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy participants Exclusion Criteria: Cannot tolerate heat pain applied to the forearm/leg, based on a calibration task at the beginning of the experiment

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 55 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Intervention Model: Single Group Assignment
Interventional Model Description: Within-participant design with behavioral manipulations.
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: N-of-few Study of Pain<br> | Behavioral: Symbolic conditioning<br>* Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) through symbolic conditioning (no actual heat stimuli, only pictures of thermometers)<br>Behavioral: Conditioning<br>* Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from experience (with actual heat stimuli).<br>Behavioral: Instructions<br>* Participants will learn associations between cues and thermal stimuli with varying temperatures (low vs. high) from verbal instructions.<br>Behavioral: Counterfactual<br>* Thermal stimuli will be either the better outcome or the worse outcome out of two possible outcomes.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Within Participant Subjective Ratings of Acute Thermal Pain Following High Compared to Low Cues (Learned Via Symbolic Learning) | Each session of the experiment includes pain tasks, in which multiple thermal stimuli are delivered. Following each thermal stimulus, participants are asked to rate how painful it was, on a semi-circular computerized scale. Ratings are based on the angle (0-180), with higher angle representing higher pain ratings. In the symbolic learning procedure, cues are conditioned to different temperatures based on pictures of thermometers (instead of actual thermal stimuli as in the conditioning procedure). For the cues that were learned via symbolic learning, the investigators will compare the average rating of pain for stimuli that are preceded by high cues minus the average rating of pain for stimuli that are preceded by low cues (each averaged across sessions), within participant. | Measured repeatedly during pain tasks, in each of the 10 sessions of the experiment (up to 3 sessions per week, depending on the participants' availability), immediately after thermal stimuli. Averaged across sessions and compared across conditions. | 
| Within Participant Subjective Ratings of Acute Thermal Pain Following High Compared to Low Cues (Learned Via Conditioning) | Each session of the experiment includes pain tasks, in which multiple thermal stimuli are delivered. Following each thermal stimulus, participants are asked to rate how painful it was, on a semi-circular computerized scale. Ratings are based on the angle (0-180), with higher angle representing higher pain ratings. In the conditioning procedure, cues are conditioned to different temperatures by delivering thermal stimuli with different temperatures after cues are presented (higher temperature following high cues and lower temperature following low cues). For the cues that were learned via conditioning, the investigators will compare the average rating of pain for stimuli that are preceded by high cues minus the average rating of pain for stimuli that are preceded by low cues (each averaged across sessions), within participant. | Measured repeatedly during pain tasks, in each of the 10 sessions of the experiment (up to 3 sessions per week, depending on the participants' availability), immediately after thermal stimuli. Averaged across sessions and compared across conditions. | 
| Within Participant Subjective Ratings of Acute Thermal Pain Following High Compared to Low Cues (Learned Via Instructions Only) | Each session of the experiment includes pain tasks, in which multiple thermal stimuli are delivered. Following each thermal stimulus, participants are asked to rate how painful it was, on a semi-circular computerized scale. Ratings are based on the angle (0-180), with higher angle representing higher pain ratings. In the instructions only condition, cues are learned via verbal suggestion. For the cues that were learned via instructions only, the investigators will compare the average rating of pain for stimuli that are preceded by high cues minus the average rating of pain for stimuli that are preceded by low cues (each averaged across sessions), within participant. | Measured repeatedly during pain tasks, in each of the 10 sessions of the experiment (up to 3 sessions per week, depending on the participants' availability), immediately after thermal stimuli. Averaged across sessions and compared across conditions. | 
| Within Participant Subjective Ratings of Acute Thermal Pain, When it is the Worse vs. the Better Alternative | In the counterfactual task, participants are presented with two alternatives (either two pain levels, or one pain level and either losing or gaining a certain amount of money). In these pairs of alternatives, the medium level pain is sometimes the better option (i.e., when the alternative is losing money or a more intense pain stimulus) and sometimes the worse option (i.e., when the other alternative is gaining money or a less intense pain stimulus). One of the two options is chosen by the computer (participants have no control on this choice). The investigators will compare the pain ratings (scale 0-180) within participant for the same level pain stimulus (medium intensity) when it is the worse vs. the better option. | Measured repeatedly during pain tasks, in each of the last 4 sessions of the experiment, immediately after thermal stimuli. Averaged across sessions and compared across conditions. |