Concept · Cognitive Bias: Decision-making and judgment biases
Possibility effect
Origin: Kahneman & Tversky, 1979
Biological Parallel
Meerkats maintain vigilance for predators despite attacks being rare—under 1% of sentinel shifts. Rare catastrophes (predation, drought, starvation) shaped evolution disproportionately because one occurrence ends your genetic line. Animals overweight tail risks: the possibility effect. Your fear of unlikely plane crashes or shark attacks reflects millions of years encoding 'rare but fatal' deeper than 'common but minor.'