Attention, unpredictability, and reports of physical symptoms: eliminating the benefits of predictability.

Sometimes unpredictable aversive events have more adverse consequences than predictable aversive events and sometimes not. Three experiments were conducted to test an attentional explanation of the inconsistent effects of unpredictability. This explanation suggests that unpredictable events exert a deleterious influence because more attention is typically directed to them. If there were no difference in the amount of attention directed to unpredictable and predictable events, however, there should be no difference in their effects. The validity of these notions was assessed by applying them to one previously established finding from the unpredictability literature--the finding that exposure to unpredictable noise leads to reports of more severe physical symptoms than does exposure to predictable noise. In Experiment 1, subjects performed a reaction time task while they listened to loud bursts of either predictable or unpredictable noise. As expected, reaction times were slower when the noise was unpredictable than when it was not. This finding suggests that more attention had been directed to the unpredictable than the predictable noise. In Experiments 2 and 3, subjects were exposed to either predictable or unpredictable noise and were either instructed to attend to the noise or given no special instructions. In both cases, subjects not instructed to attend to the noise reported more severe symptoms when the noise was unpredictable than when it was not, thus replicating the previous finding. Of greater interest, however, was the fact that equating the amount of attention directed to the unpredictable and predictable noise (by asking subjects to attend to the noise) eliminated the apparent benefits of predictability. The discussion of the findings centers on their theoretical and practical significance.