Figure 1. The metacognitive control of decisions.

First, automatic processes provide a ‘pre-effort’ belief about option values. This belief is probabilistic, in the sense that it captures an uncertain prediction regarding the to-be-experienced value of a given option. This pre-effort belief serves to identify the anticipated impact of investing costly cognitive resources (i.e., effort) in the decision. In particular, investing effort is expected to increase decision confidence beyond its pre-effort level. But how much effort it should be worth investing depends upon the balance between expected confidence gain and effort costs. The system then allocates resources into value-relevant information processing up until the optimal effort investment is reached. At this point, a decision is triggered based on the current post-effort belief about option values (in this example, the system has changed its mind, i.e., its preference has reversed). Note: we refer to the ensuing increase in the value difference between chosen and unchosen items as the ‘spreading of alternatives’ (cf. Materials and methods section).