The unlikelihood effect: When knowing more creates the perception of less

Area of Science:

• Cognitive Psychology
• Decision Science
• Risk Perception

Background:

• Individuals frequently encounter detailed information when making decisions involving risk.
• Existing research suggests that detailing causes of an outcome can increase its perceived likelihood.
• Policy and health communications often list causes to inform decision-making.

Purpose of the Study:

• To investigate a novel mechanism influencing the perceived likelihood of outcomes.
• To examine how information about causal pathways affects subjective risk perception.
• To understand how individuals integrate probabilistic information under uncertainty.

Main Methods:

• Conducted seven primary and six supplementary experimental studies.
• Presented participants with information about the probabilities of pathways leading to an outcome.
• Assessed participants' estimated likelihood of the outcome, controlling for objective probability.

Main Results:

• A novel 'unlikelihood' bias was observed: estimated outcome likelihood decreased upon learning about lower-probability causal pathways.
• This bias persisted even when the total objective probability of the outcome was explicitly communicated.
• Awareness of low-probability pathways reduced subjective risk perception, irrespective of outcome valence (positive or negative).

Conclusions:

• Understanding causal pathways can counterintuitively decrease the perceived likelihood of an outcome.
• This 'unlikelihood' bias challenges previous assumptions about information integration in risk assessment.
• Findings offer new insights into the cognitive processes underlying subjective perceptions of risk and uncertainty.