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Individuals should strategically shift decision criteria when there are disproportionate likelihoods or consequences for falsely identifying versus missing target items. Despite being explicitly aware of the advantages for criterion shifting, people on average do not shift extremely, leading many theories to conclude that people are generally suboptimal at placing decision criteria. However, assessments of individual differences reveal that some people do shift criteria quite well while others fail to shift entirely. These individual differences are remarkably consistent across time, tasks, and decision domains, yet cannot be adequately explained by other cognitive or personality measures—the degree to which people shift a criterion is a stable, uniquely individualistic cognitive trait. Individuals who inadequately shift criteria are capable of shifting to greater extents but appear unwilling to do so. Understanding criterion shifting tendencies at the individual level is vital since assessments of group averages fail to capture the true nature of this behavior. These individual differences carry important implications for investigating the neural mechanisms that underly the placement of a decision criterion.The role of the decision criterion is often neglected in neuroimaging studies. For instance, widespread frontoparietal activity is consistently observed in recognition memory tests that compare studied (“target”) versus unstudied (“nontarget”) responses. However, there are conflicting accounts that ascribe various aspects of frontoparietal activity to mnemonic evidence versus decisional processes. According to Signal Detection Theory, recognition judgments require individuals to decide whether the memory strength of an item exceeds a decision criterion for reporting previously studied items. Yet, most fMRI studies fail to manipulate both memory strength and decision criteria, making it difficult to appropriately identify frontoparietal activity associated with each process. Systematic manipulations of criteria and discriminability revealed that maintaining a conservative versus liberal decision criterion drastically affects frontoparietal activity in target versus nontarget response contrasts, whereas changes in discriminability showed virtually no differences. Findings from dense-sampling fMRI data revealed multiple frontoparietal networks associated with inhibiting prepotent responses whereas the default mode network is relatively more engaged when participants provide a prepotent response. This supports a response bias account of recognition memory indicating that widespread frontoparietal activity observed during recognition memory tests is largely attributable to decisional processes. Attempts to modulate decision criteria using neurostimulation have unfortunately failed to provide a causal link between frontoparietal activity and criterion placement, despite the robust fMRI correlates suggesting that such a relationship should exist.