Heightened likelihood of choice option selection by adding one or more unattractive/unappealing choice options. (See Asymmetrically Dominated Choice.)
Source: Behavioral Science Lab, 2017
Choices often occur relative to what is on offer rather than based on absolute preferences. The decoy effect is technically known as an ‘asymmetrically dominated choice’ and occurs when people’s preference for one option over another changes as a result of adding a third (similar but less attractive) option.
Source: Behavioral Economics