Disentangling computational and neural mechanisms of evaluation direction in value-based decision-making

Most value-based decision-making research rests on the implicit assumption that individuals typically evaluate options based on subjective preferences, favoring high-value alternatives. However, in certain contexts, the focus of information evaluation during decision-making processes may shift toward low-value evidence rather than high-value evidence. These two evaluation directions may dynamically alternate within a single decision episode to support the final decision. Yet prior studies have rarely disentangled these evaluation modes, which has limited our understanding of the cognitive and neural dynamics underlying changes in evaluation direction. This study recruited 36 participants and employed a value-based binary choice paradigm manipulating evaluation direction via task framing. While decision outcomes did not significantly differ across conditions, distinct computational and neural signatures emerged. Specifically, behavioral indicators and a hierarchical drift diffusion model (HDDM) revealed that low-value-directed evaluations were associated with longer reaction times, slower evidence accumulation, and higher decision thresholds, indicating increased deliberation. Electroencephalography (EEG) results further showed enhanced N200 and centro-parietal positivity (CPP) amplitudes in the low-value condition, reflecting greater value conflict and diminished value integration efficiency; simultaneously, increased alpha and beta desynchronization suggested heightened demand of attentional resources and stronger decision commitment. Together, these results demonstrate that value evaluation direction modulates the decision-making process across distinct temporal periods-from early value conflict to late-stage evidence accumulation and action preparation, revealing the underlying mechanisms of humans' flexible value encoding and providing a new methodological framework for analyzing multi-level value construction.