A neural representation of categorization uncertainty in the human brain (Neuron, 2006) – Dorsal medial prefrontal cortex, anterior insula, and ventral striatum activation is proportional to decision uncertainty after controlling for non-specific effects of response time. Frontal and parietal eye fields were uncorrelated to decision uncertainty.
Detection of time-varying signals in event-related fMRI designs (Neuroimage, 2008) – Reaction time is a major confound in neuroimaging studies of decision-making. Using impulse functions to model reaction time confounds is inefficient, biased, and requires physiologically implausible assumptions, specifically that the decision process is infinitesimally short. A better option is to assume that the duration of the decision process is proportional to reaction time and to explicitly model this duration in the regression model as a boxcar.
The dorsal medial frontal cortex is sensitive to time on task, not response conflict or error likelihood (Neuroimage, 2011) – The dorsal anterior cingulate cortex (dACC) has a larger response to incongruent than congruent decisions during selective attention tasks and this activity was used to conclude that the dACC is specialized for detecting decision-related conflict. However, previous studies have not properly controlled for non-specific effects of reaction time. After controlling reaction time, the dACC shows the same activation on congruent and incongruent trials.
Going, going, gone: characterizing the time-course of congruency sequence effects (Frontiers in Psychology, 2010) – Conflict causes a short-lived, phasic enhancement of attention.
Commentaries on The dorsal medial frontal cortex is sensitive to time on task, not response conflict or error likelihood (Neuroimage, 2011) – Commentaries by (1) Nachev, (2) Brown, and (3) Yeung, Cohen, and Botvinick, and (4) our response. Yeung et al claim that congruency of the stimulus-response is irrelevant for conflict tasks and that reaction time is equivalent to “conflict”. We respond by stating that if reaction time is the same as conflict, then the entire notion of “conflict” becomes conceptually useless. We further demonstrate that the conflict monitoring model published by these authors is internally inconsistent, producing two theoretically incompatible results.
Humans optimize decision-making by delaying decision onset (PLoS One, 2014) – Drift diffusion models of decision making assume that improvements in accuracy are made by increasing rate of evidence accumulation or the response threshold. However, if evidence accumulation is initiated prior to selective attention, then distractors can degrade performance and impair accuracy. We show that by delaying the onset time of the accumulation of sensory evidence until selective attention has completed identifying the target is a third method by which accuracy can be optimized. In addition, we created a computational model that could perform selective attention without the need for momentary adjustments in top-down control.
The importance of decision onset (Journal of Neurophysiology, 2016) – Perceptual decision making has focused on describing the “stopping rules” that terminate the integration of sensory evidence. These rules are assumed to be under cognitive control. But the onset of the decision process may be just as important and also under cognitive control.