Rafiei and Rahnev (2021) presented an analysis of an experiment in which they manipulated speed-accuracy stress and stimulus contrast in an orientation discrimination task. They argued that the standard diffusion model could not account for the patterns of data their experiment produced. However, their experiment encouraged and produced fast guesses in the higher speed-stress conditions. These fast guesses are responses with chance accuracy and response times (RTs) less than 300 ms. We developed a simple mixture model in which fast guesses were represented by a simple normal distribution with fixed mean and standard deviation and other responses by the standard diffusion process. The model fit the whole pattern of accuracy and RTs as a function of speed/accuracy stress and stimulus contrast, including the sometimes bimodal shapes of RT distributions. In the model, speed-accuracy stress affected some model parameters while stimulus contrast affected a different one showing selective influence. Rafiei and Rahnev’s failure to fit the diffusion model was the result of driving subjects to fast guess in their experiment.

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In a world of big data and computational resources, there has been a growing interest in further validating computational models of decision making by subjecting them to more rigorous constraints. One prominent area of study is model-based cognitive neuroscience, where measures of neural activity are explained and interpreted through the lens of a cognitive model. Although some early work has developed the statistical framework for exploiting the covariation between brain and behavior through factor analysis linking functions, current methods are still far from providing parsimonious accounts of high-dimensional (e.g., voxel-level) data. In this article, we contribute to this endeavor by investigating the fidelity of regularization methods such as the Lasso. Here, a combination of local and global penalty terms are applied to pressure elements of the factor loading matrix toward zero, reducing the false alarm rate. Such penalties facilitate the emergence of parsimonious network structure in the study of neural activation, giving way to clearer interpretations of high-dimensional data. We show through a set of three simulation studies and one application to real data that the Lasso can be an effective regularization method in the context of linking complex patterns of brain data to theoretical explanations of decisions. Although our analyses are specific to linking brain to behavior, the structure of the model is invariant to the type of high-dimensional data under investigation.

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