After deciding among options, decision makers exhibit an increased positive evaluation of the chosen option coupled with a decreased evaluation for those rejected, resulting in a spreading of alternatives (SoA). There has been a longstanding debate as whether SoA results from post-choice dissonance reduction, or whether it plays an instrumental role in reaching a decision. Here we introduce a novel procedure that measures SoA implicitly during the process of choice. Participants provided simultaneous value ratings for the options on offer on each trial before finalizing their choice. The results clearly demonstrate that SoA occurs before choices are finalized. Furthermore, SoA is instrumental to the choice process: it enhances choice consistency and confidence and reduces response time. The SoA generated during choice is transient in nature, partially regressing toward baseline shortly afterwards.
Neural Mechanisms of the Postdecisional Spreading-of-Alternatives Effect: EEG Study
