Summary: Detailed knowledge of probabilities can make dangerous risks much less risky, a new study reports.
The COVID-19 pandemic has highlighted the personal and social importance as well as the challenges of risk estimation. New research from the University of California, San Diego sheds light on how people perceive risk, finding that detailed knowledge of probabilities can make risk less risky.
For example, if people are told that 27% of the population carries at least one copy of a gene that can cause Alzheimer’s disease, they may fear they have that gene. However, if you specify that it happens because 25% have one copy of the gene and 2% have two copies of the gene, the subjective perception of risk becomes less urgent. Yet it is still true that 27% of people carry a gene that could lead to Alzheimer’s disease.
“There’s something about learning about these individual probabilities that changes the way you think about risk and causes you to lower your estimate,” said Uma R. Karmarkar, study co-author and assistant professor of Marketing and Innovation at UC San. Diego’s Rady School of Management and School of Global Policy and Strategy.
The robust results, published in the Journal of Experimental Psychology: Generalare based on results that have been replicated in over a dozen different experiments with over 1,500 participants living across the United States
In one experiment, 390 subjects who participated in the study via Amazon’s Mechanical Turk platform were divided into three groups. All groups were told that “each person has a 58% chance of getting a flea bite that causes a newly discovered bacterial infection.”
Then two groups received more specific information. One group saw that bites could come from different types of fleas, leading them to believe that a flea bite was more likely. A different group saw the different types of fleas and the probability of a bite of each type – receiving the explicit probability information led them to perceive the initial warning as less likely to occur.
“Giving all of these independent reasons with their probabilities may seem to improve recognition of the significance of an event, but may actually decrease the overall risk,” Karmarkar said. “When this happens, the ‘unlikely effect’ comes into play. One thing this means is that providing specific information about the odds can help alleviate the fear of negative outcomes.
Although the study focused on health risks, the authors also tested the theory using potential positive outcomes, such as winning the lottery. Along with the overall probability of hitting the jackpot, some topics were given additional information, such as “if I pull a colored ball out of this urn, you’ll win $50.” This additional information made the subjects perceive themselves as less likely to win. In positive scenarios, the “unlikely effect” still holds.
Karmakar notes that how institutions and policy makers provide information on health risks has become increasingly crucial.
“When communicating about risk, it is important to keep in mind the purposes for providing this information and the behaviors it is intended to elicit,” she said. “This research can help policy makers refine their messages to ensure their communications have an impact.”
About this psychology research news
Original research: Access closed.
“The improbability effect: when knowing more creates the perception of less” by Uma R. Karmarkar et al. Journal of Experimental Psychology: General
The improbability effect: when knowing more creates the perception of less
People are faced with increasingly detailed information related to a range of risky decisions. To help individuals think about these risks, various forms of health policies and messages often list their causes.
While some previous publications suggest that adding information about the causes of an outcome increases its perceived probability, we identify a new mechanism by which the reverse regularly occurs.
Across seven primary experiments and six additional experiments, we find that the estimated probability of an outcome decreases when people learn about the (by definition lower) probabilities of pathways that lead to that outcome.
This ‘improbability’ bias exists despite explicit communication of the full objective probability of the outcome and occurs for both positive and negative outcomes. Indeed, knowledge of a low-probability pathway decreases subjective perceptions of the probability of the outcome even when its addition objectively increases the true probability of the outcome.
These findings advance current understanding of how people integrate information under uncertainty and derive subjective perceptions of risk.