The Leaky Integrating Threshold and its impact on evidence accumulation models of choice RT

Verdonck, S., Loossens, T. and Philiastides, M. G. (2021) The Leaky Integrating Threshold and its impact on evidence accumulation models of choice RT. Psychological Review, 128(2), pp. 203-221. (doi: 10.1037/rev0000258) (PMID:32915011)

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Abstract

A common assumption in choice response time (RT) modeling is that after evidence accumulation reaches a certain decision threshold, the choice is categorically communicated to the motor system that then executes the response. However, neurophysiological findings suggest that motor preparation partly overlaps with evidence accumulation, and is not independent from stimulus difficulty level. We propose to model this entanglement by changing the nature of the decision criterion from a simple threshold to an actual process. More specifically, we propose a secondary, motor preparation related, leaky accumulation process that takes the accumulated evidence of the original decision process as a continuous input, and triggers the actual response when it reaches its own threshold. We analytically develop this Leaky Integrating Threshold (LIT), applying it to a simple constant drift diffusion model, and show how its parameters can be estimated with the D*M method. Reanalyzing 3 different data sets, the LIT extension is shown to outperform a standard drift diffusion model using multiple statistical approaches. Further, the LIT leak parameter is shown to be better at explaining the speed/accuracy trade-off manipulation than the commonly used boundary separation parameter. These improvements can also be verified using traditional diffusion model analyses, for which the LIT predicts the violation of several common selective parameter influence assumptions. These predictions are consistent with what is found in the data and with what is reported experimentally in the literature. Crucially, this work offers a new benchmark against which to compare neural data to offer neurobiological validation for the proposed processes.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Philiastides, Professor Marios
Authors: Verdonck, S., Loossens, T., and Philiastides, M. G.
College/School:College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
Journal Name:Psychological Review
Publisher:American Psychological Association
ISSN:0033-295X
ISSN (Online):1939-1471
Published Online:10 September 2020
Copyright Holders:Copyright © 2020 American Psychological Association
First Published:First published in Psychological Review 128(2): 203-221
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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