Public understanding and scientific uncertainty: The communication of risk in the L'Aquila earthquake

On April 6, 2009, a magnitude 6.3 earthquake struck L'Aquila, Italy, causing extensive damage and loss of life, and raising significant issues around the communication of scientific risk. In the preceding weeks, increased seismic activity had alarmed the population, prompting authorities to seek expert advice. Public authorities reassured the population that the chances of a dangerous shock were slim. These assurances given by officials led many to remain in their homes when the earthquake struck. The subsequent legal actions against the scientists involved ignited a global debate on the responsibilities and challenges in scientific communication. This paper explores the complexities of conveying probabilistic risk information to the public and decision-makers. It highlights how different formats for presenting probabilistic data can significantly influence understanding and decision-making. In particular, it canvasses how the use of natural frequencies to convey probabilistic information makes it cognitively easier to understand and manipulate them, given how they make more salient and transparent the so-called base rate. However, the benefits of using natural frequencies decrease when dealing with low-probability, high-consequence (LPHC) events like major earthquakes, where even significant increases in relative probability remain small in absolute terms. Moreover, the paper investigates the social dimensions of earth science, examining the multifaceted role of scientists as both technical experts and social actors. The L'Aquila case exemplifies the need for integrating scientific accuracy with an understanding of its social implications. Effective risk communication must address cognitive limitations and the presence of social context to reach appropriate public behavioral responses. In order to achieve that, communication should be handled by actors that have specific expertise in its complexity.