Ordered to attract: The dynamics of attraction effect in simultaneous and sequential value-based choice tasks

The attraction effect (AE) occurs when the introduction of a dominated option (decoy) increases the likelihood of choosing a target over a competitor. While this effect is well established, less is known about how presentation format shapes its emergence. In this study, participants made value-based choices with probabilistic monetary outcomes, under two conditions: simultaneous presentation of all three options and sequential presentation of options one at a time. In the simultaneous condition, AE emerged only when the target and decoy were spatially adjacent, indicating that visual proximity is critical for revealing the decoy’s inferiority and enhancing the target’s attractiveness. When the competitor was positioned between them, the effect disappeared. In the sequential condition, by contrast, AE was consistently observed regardless of presentation order, suggesting that direct visual juxtaposition may be less critical in this setting. Overall, these findings show that AE in simultaneous choices depends on spatial arrangement, whereas in sequential value-based choices it persists across orders. These results suggest that comparison-based processes may operate differently across presentation formats, advancing understanding of how context effects unfold in decision-making.