On the nature of certainty in value-based decisions: Disentangling variability- and extremity of experiences

Consistent value-based decision-making is crucial for outcomes such as
maintaining a healthy lifestyle, or being perceived as trustworthy.
Confidence in evaluations is related to consistency of value-based
decisions, but its nature is poorly understood. Here we examined how
evaluation confidence is formed through the possibly unique contributions
of “variability”- and “value-extremity” of prior experiences with objects.
We conducted a preregistered 2×2 within-subjects experiment (N = 188)
where variability- and value-extremity of experiences with objects were
manipulated independently. Participants learned value-distributions for
objects, estimated their value, and rated confidence in their evaluation.
As predicted, results show that variability of experiences is negatively
related to confidence, independent of value-extremity. Surprisingly, we
find no evidence for a positive effect of value-extremity on evaluation
confidence. These results point to the possibility that the previously
observed relation between value-extremity and evaluation confidence is the
result of an ecological confound between variability and “value-extremity”
of prior experiences.