Three Pillars of Prospect Theory

Key Insight

Prospect theory is built upon three core cognitive features that significantly influence how individuals evaluate financial outcomes, functioning as operating characteristics of System 1. The first is that all evaluations are relative to a neutral reference point, often the current status quo, but sometimes an expected or deserved outcome like a bonus or raise. Outcomes superior to this reference point are perceived as gains, while those falling below it are experienced as losses.

The second principle is diminishing sensitivity, which applies to both sensory perceptions and changes in wealth. This means the subjective impact of a change lessens as the base magnitude increases. For example, the psychological difference between gaining $900 and $1,000 is much smaller than the difference between $100 and $200. Graphically, this is represented by an S-shaped value function, indicating that sensitivity diminishes for both gains and losses.

The third and most impactful principle is loss aversion. When positive and negative outcomes are directly compared, losses consistently loom larger than gains. This asymmetry is profound; the response to a loss is stronger than the response to a corresponding gain. This bias has an evolutionary history, as organisms prioritizing threats over opportunities generally have better chances of survival and reproduction, and it is reflected in the value function's steeper slope in the negative domain compared to the positive domain.