Availability heuristic. What is the frequency of a category? if their retrieval is easy and fluid, the category will be judged extensive.

In 2009 the so-called influenza A (H1N1) pandemic began in Spain and  lasted until april 2010 when data were las updated. More than 1,500 cases were officially confirmed and approximately 300 people died. We all remember the informational, political deployment of social measures, there were posters, dispensers of antiseptic gel…everywhere.

In 2014 Ebola appeared in Spain in several cases: repatriations of some infected people in Africa, a contagion of a nursing assistant and several false alarms. Also on this occasion we can remember the informative news in all media with minute by minute updates, press conferences (there were many), political and social protests… In this case there was one death.

In both cases the detailed description of what was happening, in the media, turned A 2009 Flu and the Ebola crisis in 2014 into the social concern and alarm of this country.

Flu in 2017, It´s just common ´flu!

Flu related deaths in Barcelona exceed all forecasts. La Vanguardia In the first week of the year (2017) there have been more than 250 deaths linked to the epidemic, which surpass the two standard deviations from the expected value informe de la Generalitat

sesgo disponibilidad.alarma social

Heuristic of availability.

  • We find the heuristic of availability. What is the frequency of a category? For example contagion of influenza A or Ebola. The answer is that if the class examples are extracted from memory, if their retrieval is easy and fluid (absolutely everithing, all television news, all newspapers from those dates), the category will be judged extensive. We make no judgement, we manifest the ease with which the examples come to mind. Dramatic events, personal experiences, photographs, videos … will be more available than simple words or statistics.
  • Being vigilant about bias is very boring, but the possibility of avoiding an error that does not suit us justifies the effort, as Kahneman tells us. In a study by Slovic, Lichtenstein and Flischoff, “Knowing with certainty: the appropriateness of extreme confidence”, it is shown that many times we are very often mistaken. They showed that we think that death by accident is more likely than by a stroke, when it is twice that. Or death from illness is 18 times more likely than accident, when judged equally. This shows that the causes of death are distorted by media coverage and this is biased towards novelty, drama, exoticism. Certain issues receive disproportionate coverage and attention, and our expectations about the frequency of events are distorted by the prevalence and emotional intensity of messages.

Cascade of availability. Public opinión is important like the expert management.

A cascade of availability is a self-reinforcing process of collective belief formation through which an expressed perception triggers a chain reaction that gives the perception of increasing plausibility through its increasing availability in public discourse. The driving mechanism involves a combination of information and reputation motives: Individuals support perception in part by learning from the apparent beliefs of others and partly by distorting their public responses in the interest of maintaining social acceptance.

Availability entrepreneurs – activists who manipulate the content of speech to trigger cascades of availability that can advance in their agendas. Their availability campaigns can generate social benefits, but sometimes they cause harm, which suggests a need for safeguards. Focusing on the role of mass pressures in regulating the risk associated with production, consumption and the environment, teachers Timur Kuran and Cass R. Sunstein analyze the availability of “helmets” and suggest reforms to alleviate their potential dangers. Their proposals include new government structures designed to give officials better instruction against massive demands for regulatory changes and a readily available scientific database to reduce reliance on popular perceptions.


Kuran, Timur; Cass R Sunstein (2007). “Availability Cascades and Risk Regulation”. The Law School of the University of Chicago.