We show that EEG stimulus-locked negative peaks occurring between 150 and
275 milliseconds (N200 latencies) reflect visual processing time that
occurs before evidence accumulation, labeled visual encoding time (VET), in
the context of drift-diffusion theory of human decision making of reaction
time and choice. VET was found to be a component of non-decision time,
allowing accurate time measurements of VET, decision-time, and residual
motor response during decision-making. We confirm this finding across
multiple subjects by directly testing 1-to-1 relationships between EEG
potentials and non-decision time parameters with Bayes Factors using the
Savage-Dickey ratio, calculated from posterior distributions of
hierarchical Bayesian parameters. We also directly test this hypothesis by
quantifying 1-to-1 slope relationships in linear regression between EEG
potentials and reaction time percentiles, methods more immune to
contaminant trials due to subject mind-wandering. By confirming VET as the
first component of non-decision time, we then estimate residual motor
response time. These combined neurocognitive techniques (merging Cognitive
Neuroscience techniques with Mathematical Psychology theory) add to
existing knowledge of the chronometry of human neural networks and allow
accurate measurement of processing stages during simple human decision
making.