Cognitive models are mathematical frameworks providing a quantitative account of cognitive mechanisms underlying an individual’s behavior. This line of research has followed three key areas: 1. approaches towards constraining cognitive models for more reliable estimates (Molloy et al., 2018), 2. leveraging joint models to uncover mechanisms central to conflict processing (Molloy et al., 2025), and 3. applying cognitive modeling frameworks to study delay discounting (Molloy et al., 2020; Turner et al., 2019). Overall, modeling can improve psychometric properties of behavior and uncovers distinct cognitive processes that relate to individual differences.
References
2025
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Joint Cognitive Models Reveal Sources of Robust Individual Differences in Conflict Processing
M Fiona Molloy, Taraz Lee, John Jonides, Han Zhang, Jacob Sellers, Andrew Heathcote, Chandra Sripada, and Alexander Weigard
Jun 2025
Experimental manipulations in conflict tasks, e.g., the Stroop, Flanker, and Simon tasks, lead to systematically poorer performance in “incongruent” conditions that feature stimuli that contradict task goals. However, substantial recent debate surrounds whether individual differences in conflict task behavior reflect reliable, trait-like mechanistic processes. Much prior work uses difference scores, contrasting performance between incongruent and congruent trials to index conflict suppression ability, but recent work demonstrates these scores exhibit poor psychometric properties. Formal cognitive process models suggest that individual differences in conflict suppression are driven by task-general processes, as opposed to processes specialized for conflict. However, this prior work separately models cognitive process parameters and their covariation, which fails to adequately account for measurement error. Here, we model distinct mechanisms of conflict task performance and their covariance simultaneously using hierarchical Bayesian joint modeling methods for the first time which improves individual estimation and accounts for error. We fit the conflict linear ballistic accumulator model (LBA) to two large datasets containing multiple conflict tasks and test-retest sessions, and an additional large dataset containing a conflict task and simple perceptual decision-making task. First, within conflict tasks, we found moderate test-retest reliability for both conflict-specific processing mechanisms, and, to a larger degree, task-general mechanisms. Second, task-general, but not conflict-specific, mechanisms were correlated across different conflict tasks. Third, these task-general mechanisms were correlated between conflict tasks and a simple decision-making task without conflict suppression demands. Overall, we found robust individual differences in computational mechanisms underlying general decision-making, but not mechanisms specific to conflict processing.
2020
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Hierarchies improve individual assessment of temporal discounting behavior.
M. Fiona Molloy, Ricardo J. Romeu, Peter D. Kvam, Peter R. Finn, Jerome Busemeyer, and Brandon M. Turner
Decision, Jun 2020
Publisher: US: Educational Publishing Foundation
2019
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On the Neural and Mechanistic Bases of Self-Control
Brandon M Turner, Christian A Rodriguez, Qingfang Liu, M Fiona Molloy, Marjolein Hoogendijk, and Samuel M McClure
Cerebral Cortex, Feb 2019
Intertemporal choice requires a dynamic interaction between valuation and deliberation processes. While evidence identifying candidate brain areas for each of these processes is well established, the precise mechanistic role carried out by each brain region is still debated. In this article, we present a computational model that clarifies the unique contribution of frontoparietal cortex regions to intertemporal decision making. The model we develop samples reward and delay information stochastically on a moment-by-moment basis. As preference for the choice alternatives evolves, dynamic inhibitory processes are executed by way of asymmetric lateral inhibition. We find that it is these lateral inhibition processes that best explain the contribution of frontoparietal regions to intertemporal decision making exhibited in our data.
2018
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What’s in a response time?: On the importance of response time measures in constraining models of context effects.
M. Fiona Molloy, Matthew Galdo, Giwon Bahg, Qingfang Liu, and Brandon M. Turner
Decision, Feb 2018
Publisher: US: Educational Publishing Foundation