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    Using time-varying evidence to test models of decision dynamics: bounded diffusion vs. the leaky competing accumulator model

    Tsetsos, Konstantinos and Gao, J. and McClelland, J.L. and Usher, Marius (2012) Using time-varying evidence to test models of decision dynamics: bounded diffusion vs. the leaky competing accumulator model. Frontiers in Neuroscience 6 (79), pp. 6-79. ISSN 1662-453X.

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    Abstract

    When people make decisions, do they give equal weight to evidence arriving at different times? A recent study (Kiani et al., 2008) using brief motion pulses (superimposed on a random moving dot display) reported a primacy effect: pulses presented early in a motion observation period had a stronger impact than pulses presented later. This observation was interpreted as supporting the bounded diffusion (BD) model and ruling out models in which evidence accumulation is subject to leakage or decay of early-arriving information. We use motion pulses and other manipulations of the timing of the perceptual evidence in new experiments and simulations that support the leaky competing accumulator (LCA) model as an alternative to the BD model. While the LCA does include leakage, we show that it can exhibit primacy as a result of competition between alternatives (implemented via mutual inhibition), when the inhibition is strong relative to the leak. Our experiments replicate the primacy effect when participants must be prepared to respond quickly at the end of a motion observation period. With less time pressure, however, the primacy effect is much weaker. For 2 (out of 10) participants, a primacy bias observed in trials where the motion observation period is short becomes weaker or reverses (becoming a recency effect) as the observation period lengthens. Our simulation studies show that primacy is equally consistent with the LCA or with BD. The transition from primacy-to-recency can also be captured by the LCA but not by BD. Individual differences and relations between the LCA and other models are discussed.

    Metadata

    Item Type: Article
    Additional Information: This Document is Protected by copyright and was first published by Frontiers. All rights reserved. it is reproduced with permission.
    Keyword(s) / Subject(s): bounded diffusion, LCA, perceptual choice, non-stationary evidence, order effects
    School: Birkbeck Schools and Departments > School of Science > Psychological Sciences
    Depositing User: Sarah Hall
    Date Deposited: 17 Dec 2015 16:36
    Last Modified: 27 Jul 2019 18:23
    URI: http://eprints.bbk.ac.uk/id/eprint/13818

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