Drift-Diffusion Models (DDMs) are a widely-used class of models that assume an accumulation of evidence during a quick decision. These models are often used as measurement models to assess individual differences in cognitive processes, such as an individual's evidence accumulation rate and response caution. An additional underlying assumption of these models is that there is internal noise in the evidence accumulation process. However, fitting DDMs to experimental choice-response time data alone cannot yield estimates of an individual's evidence accumulation rate, caution, and internal noise at the same time. This is due to an intrinsic joint-unidentifiability of these parameters when fitting DDMs to behavioral data. We introduce methods of estimating these parameters at the same time with additional data types. The methods to estimate model parameters rely on Bayesian inference and simulation-based Bayesian inference. We show why these methods are useful without making strong assumptions.

SOB-CS is an interference-based computational model ofworking memory that explains findings from simple and com-plex span experiments. According to the model’s mechanismof interference by superposition, high similarity between mem-ory items and subsequently processed distractors is beneficialbecause the more a distractor is similar to an item, the morethey share similar units, leading to less distortion of the mem-ory item. When time allows, SOB-CS removes interfering dis-tractors from memory by unbinding them from their context.The combination of these two mechanisms leads to the predic-tion that when free time is long enough to remove the distrac-tors entirely, similarity between items and distractors shouldno longer be beneficial to memory performance. The aim ofthe present study was to test this prediction. Adult participantsperformed a complex-span task in which the free time follow-ing each distractor and the similarity between items and dis-tractors were varied. As predicted by the model, we observeda positive effect of the similarity between items and distrac-tors, and a negative effect of pace on the mean working mem-ory performance. However, we did not observe the predictedinteraction. An analysis of the errors produced during recallshowed that longer free time reduced the tendency of distrac-tors to intrude in recall much less than the model predicted.The SOB-CS model accounted well for the data after a sub-stantial reduction of the removal-rate parameter.