The context of a noxious stimulus affects the pain it evokes

The influence of contextual factors on the pain evoked by a noxious stimulus is not well defined. In this study, a −20°C rod was placed on one hand for 500ms while we manipulated the evaluative context (or ‘meaning’) of, warning about, and visual attention to, the stimulus. For meaning, a red (hot, more tissue damaging) or blue (cold, less tissue damaging) visual cue was used. For warning, the stimulus occurred after the cue or they occurred together. For visual attention, subjects looked towards the stimulus or away from it. Repeated measures ANCOVA was significant (α=0.0125). Stimuli associated with a red cue were rated as hot, with the blue cue as cold (difference on an 11 point scale ∼5.5). The red cue also meant the pain was rated as more unpleasant (difference ∼3.5) and more intense (difference ∼3). For stimuli associated with the red cue only, the pain was more unpleasant when the stimulus occurred after the cue than when it didn’t (difference ∼1.1). Pain was rated as more intense, and the stimulus as hotter, when subjects looked at the red-cued stimulus than when they didn’t (difference ∼0.9 for pain intensity and ∼2 for temperature). We conclude that meaning affects the experience a noxious stimulus evokes, and that warning and visual attention moderate the effects of meaning when the meaning is associated with tissue-damage. Different dimensions of the stimulus’ context can have differential effects on sensory-discriminative and affective-emotional components of pain.