Domain-specific overall value effects on choice behaviors and eye-movements

The impact of value difference on response times (RTs) is well established, but recent research has shown that RTs are lower when the overall value/intensity across all options is higher: choosing between two very attractive / high-intensity options leads to faster decisions than choosing between two less attractive / low-intensity options. Whereas the overall value effect on RT appears to be robust and generalized across various decision types, little is known about its effect on choice accuracy and eye movements. The present study investigates the computational mechanisms underlying the impact of the overall value of available options on decision-making. We used attentional drift-diffusion model (aDDM) to simulate decision-making under different levels of overall value, and found that the overall value was predicted to reduce choice accuracy (together with RT) regardless of choice domains. To test these predictions empirically, we conducted a 3 (OV: sum of option values/stimulus intensities) by 3 (VD: the difference between values/stimulus intensities) by 2 (choice domain: value-based and perceptual decision) within-subject design eye-tracking experiment with n = 60 participants. Remarkably, the results were partially consistent with the model predictions but suggested a high degree of domain-specificity of overall value effects. In particular, we found that accuracy rates were significantly lower at a medium OV level compared to high and low levels in the value-based decision only, while accuracy in perceptual decision was not significantly changed by overall value manipulation. With respect to eye-tracking, OV similarly affected fixation patterns across choice domains: middle and final fixation durations were significantly decreased from low to high OV. However, we observed that OV adjusted the relationship between the final fixation and the choice in value-based decisions only: the tendency of choosing the last fixated option (i.e., snack) was increased when OV was decreased. Together, our results suggest that overall value is involved in the choice process and different cognitive mechanisms are needed to capture domain-specific impacts of overall value on choice accuracy, final fixation bias and their interactions.