Don’t Scare the Public With Vague Warnings

Should the government issue public warnings as part of its strategy to prevent terrorist attacks?

At first glance, many would emphatically say “yes.” After all, the government collects intelligence to combat terrorism, and this information is crucial for threat assessments in the military and law enforcement. Why should the government withhold this information from its citizens?

Indeed, many in the U.S. assume that their government has a moral responsibility to warn of imminent danger. Ideally, these warnings serve a practical purpose, but they also address a deep-seated human desire to make unpredictable threats more predictable and understandable. In this context, it is important to examine how such warnings are used and whether the information is helpful.

While the war on terrorism has revealed vast, uncharted territory in the strategic world, the question of public warnings for vaguely defined threats has been explored in the realm of earthquake preparedness. From this experience, we have learned that short-term public warnings are counterproductive, especially when the threat is poorly defined.

The seeds for this insight began in the 1970s with government-sponsored efforts to predict earthquakes in the U.S. and Japan. There were extensive scientific deployments to monitor the Earth for signals of an impending earthquake. Analogous to the current war on terrorism, the monitoring provided interesting data. However, it was impossible to obtain direct information from the most important region: the source of an earthquake, deep in the Earth’s crust.

Viewed in retrospect, the research increased our understanding of earthquakes. However, it also generated unnecessary public hysteria as experts and charlatans predicted devastating earthquakes that never occurred, with many of the warnings carried in major media outlets.

From this experience, three negative effects of public warnings for vague threats became apparent:

* False alarms: Statistical uncertainty is a critical part of any prediction (for instance, there is a 50% chance of rain today). When the threat is poorly defined, the uncertainty is unbounded and fears increase exponentially. In this setting, “false alarms” make people skeptical about future warnings and the authorities providing the information. As a consequence, the warnings become less effective as false alarms increase.

* False confidence: If a government uses warnings as a threat-reduction strategy, people become complacent, waiting for last-minute information before taking action.

* Counterproductive activities: Ideally, warnings allow preemptive actions to reduce damages--for example, staying out of dangerous buildings before an earthquake. However, warnings can also stimulate activities that increase damage--such as mass pandemonium as people try to leave an area before an earthquake, jamming freeways and other escape routes.

Warnings no longer play a significant role in earthquake preparedness. In the U.S., the focus is now on stronger buildings, permanent risk-reduction measures at home and work and advanced information systems to assist rapid response in the event of a quake.

Recognizing that earthquakes are inevitable in parts of the U.S., the goal is to be prepared at all times. The benefits of this approach are twofold: Society is increasingly resilient to seismic hazards, and we do not suffer the effects of continuous warnings.

The implications for counterterrorism seem clear: We need to accept the inevitability of terrorist attacks, prepare our society to protect against them before they occur and be ready to mitigate the effects afterward. Vague warnings, such as those issued two weeks ago on the possibility of attack, are not helpful because the public cannot use the information for effective risk reduction.

As the U.S. develops its homeland defense strategy, there should be a premium on information management to ensure that warnings and associated intelligence are disseminated only to those who can play an effective role in protecting us.

Otherwise, the simple way for terrorists to disrupt American society would be to get on cell phones in a foreign country and start talking about an “imminent attack.”