nl-DDM: a non-linear drift-diffusion model accounting for the dynamics of single-trial perceptual decisions

The Drift-Diffusion Model (DDM) is widely accepted for two-alternative forced-choice decision paradigms thanks to its simple formalism, straightforward interpretation, and close fit to behavioral and neurophysiological data. However, this formalism presents strong limitations to capture inter-trial dependency and dynamics at the single-trial level. We propose a novel model, the non-linear Drift-Diffusion Model (nl-DDM), that addresses these issues by allowing the existence of several trajectories to the decision boundary. We show that the fitting accuracy of our model is comparable to the accuracy of the DDM, with the non-linear model performing better than the drift-diffusion model for an equivalent complexity. To give better intuition on the meaning of nl-DDM parameters, we compare the DDM and the nl-DDM through correlation analysis. This paper provides evidence of the functioning of our model as an extension of the DDM. Our model paves the way toward more accurately analyzing single-trial dynamics for perceptual decisions and accounts for pre- and post-stimulus influences. ### Competing Interest Statement The authors have declared no competing interest.