Earthquakes: Some Major Aftershocks May be in the Brain

Feb. 15, 2012 — -- It probably didn't seem that way at the time, but when a devastating earthquake leveled parts of Christchurch, New Zealand, two years ago, psychologists at the University of Canterbury found themselves blessed with an opportunity.

William S. Helton and James Head had completed the first half of a research project designed to measure the mental performance of 16 of their graduate students when the 7.1 magnitude quake struck on Sept. 4, 2010. Three weeks later they completed the second half of their study, providing rare insights into how a natural disaster can affect individuals in unexpected ways, contributing to mental errors that could be fatal.

Since the second half of the study was identical to the first half, the results provide a before-and-after look into cognitive decline following a natural disaster. Normally, the students would be expected to do better the second time around, because repeated exposure to simple mental tasks should improve one's performance. But instead, it was worse.

"People would find themselves zoning out and making more errors than usual after the quake," Helton said in releasing the study, to be published in the journal Human Factors.

The study adds to a small body of evidence that any disaster, caused by either nature or humans, can degrade the mental competence of the victims. Although this study is unfortunately small, as the researchers themselves admit, it does dovetail with other research conducted under very different circumstances.

One study found a significant increase in automotive accidents in the northeastern United States in the three months following the terrorist attacks of Sept. 11, 2001. At first, researchers thought the accident rate went up because people were driving instead of flying, but subsequent research showed that people were driving less, not more, during that period.

The New Zealand psychologists suggest another explanation. At least some of the drivers involved in those accidents were probably suffering from "cognitive intrusions." Or, as Helton put it, they were "zoning out" when their attention should have been on the road.

It is exactly that kind of error that the New Zealand experiment was designed to measure. Each of the participants, isolated in windowless cubicles, stared at a computer screen as a series of numbers flashed by at the rate of 48 per minute. They were instructed to either type a number as it appeared, or ignore it if it was the number 8.

Following the quake the participants missed significantly more numbers than they had before the quake, suggesting they were distracted from the test, much the same as a driver might miss a stop sign while trying to type a text message, or tend to an infant on the back seat.

The performance was even worse among participants who told the researchers they were "anxious" because of the quake.

As disasters go, however, earthquakes are unique. Unlike hurricanes, or wildfires, they strike without warning. Aftershocks can be even more disturbing than the main shock because they suggest the worst may still coming. And it seems like they might go on forever.