Methodological Issues in the Study of the Browning Prediction
November 1993 (VOL. 11, NO. 3)
We examined five methodological issues which could contaminate research on people's reactions to the Browning quake prediction: sample biases, self-selection artifacts, historical event artifacts, self-report inconsistency over time, and reactive testing effects. We found some evidence for self-selection biases in mail survey return rates, especially during the one-week period before the predicted quake. People who were threatened by the prediction were less likely to complete these surveys. There was a self-selection artifact associated with the TV movie "The Big One" and with the "Unsolved Mysteries" episode on Browning. These two shows attracted people who were already concerned about quakes and believed the prediction. After the prediction was disconfirmed, a control group of participants showed large declines in the perceived likelihood of future quakes, suggesting that either some historical artifact or simple knowledge that a scientist's prediction was wrong causes a disillusionment or "cry wolf" effect. People who lived near the New Madrid fault also manifested this decline, but it was significantly smaller than the one for the control groups. Consistency of self-reports about preparation for the predicted earthquake and the consistency of self-reports about watching the "Big One" and the "Unsolved Mysteries" episode were very high. We found no pretest sensitization effects, but we did uncover an unusual reactivity effect for surveys even after the failed prediction. We compared people surveyed immediately after the prediction failed and at a six week follow-up to those who were surveyed only at the six-weeks follow-up. Filling out the immediate-post survey had the effect of reducing concern about earthquakes on the six-week follow-up. These artifacts suggest that researchers must be cautious in generalizing from their samples, interpreting pre-post prediction changes, and claiming that media effects have significant impact on beliefs about disasters.