Ex-Gaussian vector metric and similarity index applied to reaction time analysis

In psychology and cognitive neuroscience, reaction time (RT) series and their ex-Gaussian distributions are commonly used as scalar quantities to explore the time course of attentional processes. However, we propose that such attentional processes can also be analyzed using an "ex-Gaussian vector", defined by successive triads of ex-Gaussian sigma, tau, and mu parameters from RT series. This geometrical object may help characterize interindividual differences between congruent and incongruent stimuli in the attentional Stroop task within a group of participants. To test these hypotheses, we calculated the similarity index of these geometrical objects in young adults without detectable neurological disorders. Our findings show that during two weeks of continuous Stroop task application, each participant displayed distinct ex-Gaussian RT vectors in a Cartesian 3D plot. Furthermore, our study found that the similarity index between ex-Gaussian RT vectors was significantly higher for incongruent stimuli than for congruent stimuli.