Reducing a certain outcome’s probability has greater psychological impact than reducing an already-uncertain one

Evidence

The modal preferences exhibited in the preceding two problems illustrate a phenomenon first reported by Allais (1953) that is referred to in prospect theory as the certainty effect: reducing the probability of an outcome by a constant factor has a greater impact when the outcome was initially certain than when it was merely possible. — John T. Jost and Jim Sidanius, Political Psychology, 2512

Categorization

• DEFINE: Defines the certainty effect (Allais 1953) crisply with its key counterintuitive implication.
• XREF: Connects to the systemic roots of prospect theory / loss aversion, and could link to ADDENDUM pieces on irrational decision-making in political preference formation.