Block diagram representation of a DDM for accumulating sensory evidence.

The physical stimulus omega(t) is first encoded by sensory organs (here represented by the gain K). Evidence of the stimulus property of interest (in this case stimulus intensity, computed by the abs() operation) is integrated over time (rightmost block, representing an integrator using Laplace notation). The noise signal n(t) represents physiological noise that is internal to perceptual processes and is responsible for trial-to-trial variability. In the leaky version of the DDM, a leaky integrator replaces the normal integrator (rightmost block).