Oddly Wired
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decision making

Your choice changes when an irrelevant option appears.

The decoy effect occurs when your preference between two choices shifts after a third, inferior option is introduced.

By adding a less attractive option, the choice that was previously mid-tier suddenly seems like a better value. The presence of the decoy provides a point of comparison that makes one original option look superior.

You are not choosing the best option, but the one that looks best by comparison.

Where this comes from

Study
Joel Huber and Christopher Puto, 1982
What the check found
Huber, Payne, and Puto (1982) are correctly identified as the originators of this concept, technically termed the asymmetric dominance effect.
Confidence
Solid, with limits

Related

One of these every day, and every one names the study it came from. When a finding is contested, it says so.