The decoy effect (also called the asymmetric dominance effect) occurs when the addition of a third option — one that is clearly inferior to one existing option but not to the other — systematically shifts preference toward the option that dominates the decoy. Huber et al. (1982) first demonstrated this violation of rational choice theory: in a choice between two roughly equal options A and B, adding a decoy A′ that is slightly worse than A on all dimensions causes more people to choose A over B, even though A itself has not changed.
Key Structures
- Loss Aversion — The robust finding that losses loom larger than equivalent gains — people typically feel the pain of losing something about twice as strongly as the pleasure of gaining it.
- Decision Making — The cognitive processes involved in selecting a course of action from among multiple alternatives, integrating information about options, outcomes, and preferences.
How It Works
Consider choosing between two apartments: one is cheaper but farther from work, the other is closer but more expensive. Adding a third apartment that is the same price as the closer one but even farther away makes the closer apartment look better by comparison — it now "dominates" an option, making it feel like a clearly superior choice. The decoy makes the comparison easier and provides a justification for choosing the target. This effect exploits the fact that humans evaluate options relationally rather than in absolute terms.
Mechanisms and Explanations
Several mechanisms have been proposed. The simplification account suggests people use the dominance relationship as a simplifying heuristic. The value-shift model proposes that the decoy changes the perceived value of the target attribute. The emergent-value account argues that the decoy creates a new "dominance" attribute that the target option wins on. Loss aversion also plays a role: the decoy creates a reference point against which the target option shows no losses, while the competitor does. Regardless of mechanism, the effect robustly demonstrates that preferences are not fixed — they are constructed from the choice context.
The decoy effect is widely used in pricing and product design. A classic example is subscription tiers: offering print-only ($59), digital-only ($125), and print+digital ($125) makes the print+digital option look like an obvious bargain — the print-only option serves as a decoy that makes the combo feel like a steal. The effect has been documented in consumer choice, medical decision making, hiring decisions, and even political elections, making it one of the most practically consequential biases in judgment and decision making.