Beyond conformity: Social influences on pain reports and physiology

Abstract

Social information can profoundly influence behavior, but its effects are often explained in terms of "conformity," implying effects on decision-making and communication rather than deeper sensory modulation. We examined whether information about other people's pain reports affected both participants' pain experience and skin conductance responses (SCR) during pain. Sixty volunteers experienced painful heat stimulation preceded by 2 kinds of informational cues: (a) nonreinforced social information indicating low or high pain ratings from previous participants; and (b) reinforced conditioned stimuli (CSlow, CShigh). Both high-pain social information and CShigh cues enhanced pain and SCRs relative to their respective controls, with particularly robust effects of social information. Effects of both manipulations on both pain and SCRs were mediated by trial-by-trial pain expectancies. These results demonstrate strong social influences on pain and autonomic responses, and suggest that expectations from multiple sources can influence pain physiology independent of reinforcement.

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Figures

Figure 1

Experimental design of the pain-learning task. Each trial started with the presentation of two cues. Participants were told that each of ten vertical lines on a horizontal visual analog scale (VAS) reflected the pain ratings of previous participants. This social information could either indicate low (SocialLOW) or high (SocialHIGH) others’ pain ratings. Unbeknown to participants, this information was actually not predictive of the actual stimulus temperature. Additionally, participants were presented with one of two Gabor patches with different orientation (35° and 55° angle). One gabor patch (CSLOW) was followed by low-to-medium (47 or 48°C), the other Gabor patch (CSHIGH) with medium-to-high (CH, 48 or 49°C) heat stimulation. Following the presentation of the two cues, participants had to indicate how much pain they expected and were then stimulated with short (1s) heat to the left forearm. After the heat stimulation, they had to rate on a VAS how much pain they actually felt.

Figure 2

Results of the learning task. A) Pain ratings showed significant effects of stimulus temperature, of social information, as well as cue value (CSLOW vs. CSHIGH). The bar plot illustrates the effects of interest for medium temperature trials. B) SCR to pain were also characterized by effects of temperature, as well as social information. The lower panel bar plot illustrates these effects for medium temperature trials. C and D) Multi-level mediation models demonstrated that the effects of both social information and of CS on pain report (C) and on SCR (D) were fully mediated by expectancy ratings.