Underpredicted pain disrupts more than correctly predicted pain, but does not hurt more.

One of the explanations for the negative effects of underpredicted aversive experiences is that they have more impact than correctly predicted aversive experiences. In a laboratory experiment 40 normal female subjects executed an auditory discrimination task. Subjects were randomly assigned to a correct information condition and an underprediction information condition. After ten trials (baseline) subjects were informed that they would receive some painful (correct prediction) or non-painful tingling (underprediction) stimuli during the discrimination task. Starting just before five of the following 20 discrimination trials, 2 s of painful electrical stimulation was given. Subjects rated sensations and painfulness of the electrical stimulation, subjective anxiety, and degree of distraction from the task, after each pain stimulus. Reaction times of the discrimination task and heart rate were measured. Underprediction information resulted in lower pain ratings, but stronger heart rate responses and higher disruption on the discrimination task, compared to correct information. This suggests that while underpredictions of pain do not hurt more, disruption on primary tasks and physiological impact are higher. Underpredicted pain has more impact than correctly predicted pain, not because it hurts more, but because it conveys inherent danger information.