Qualitative speed-accuracy tradeoff effects can be explained by a diffusion/fast-guess mixture model

• Published in: Scientific reports Vol. 11; no. 1; pp. 15169 - 9
• Main Authors: Ratcliff, Roger, Kang, Inhan
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 26.07.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 631/114/2397; 631/477; 631/477/2811; Accuracy; Decision Making - physiology; Diffusion; Diffusion models; Experiments; Humanities and Social Sciences; Humans; Models, Psychological; multidisciplinary; Photic Stimulation; Probability; Psychomotor Performance - physiology; Reaction Time - physiology; Science; Science (multidisciplinary); Visual Perception - physiology
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-021-94451-7

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.