Response bias reflects individual differences in sensory encoding

Abstract

Humans exhibit substantial biases in their decision making even in simple 2-choice tasks but the origin of these biases remains unclear. We hypothesized that one source of bias could be individual differences in sensory encoding. Specifically, if one stimulus category gives rise to an internal evidence distribution with higher variability, then responses should optimally be biased against that stimulus category. Therefore, response bias may reflect a previously unappreciated subject-to-subject difference in the shape of the internal evidence distributions. We tested this possibility by analyzing data from three different 2-choice tasks (N = 443, 443, 498). We found that, for all three tasks, response bias moved in the direction of the optimal criterion determined by each subject’s idiosyncratic internal evidence variability. These results demonstrate that seemingly random variations in response bias can be driven by individual differences in sensory encoding and are thus partly explained by normative strategies.

Examining the robustness of the relationship between metacognitive efficiency and metacognitive bias

“…Task 3 is from a dataset named "Rouault_2018_Expt1" (Rouault et al, 2018), which includes 498 subjects. We previously analyzed the same three tasks to investigate how bias depends on the individual variability in sensory encoding (Rahnev, 2020).…”

“…We used the same criteria for preprocessing the data as in our previous paper (Rahnev, 2020). For all tasks, we first removed all trials with reaction times lower than 200 ms or higher than 2 seconds.…”