Abstract
Reaction time (RT) is one of the most frequently used measures to detect cognitive processes. When tasks require more cognitive processes / resources, reaction is slower. However, RTs cannot provide information about the temporal sequence (or existence) of cognitive processes. For this, a temporal index is needed. Pupils respond reflexively to light but also to cognitive activation. The more cognitive resources a task requires, the more pupil dilation that can be observed. However, despite being able to use changes in pupil size as a temporal measure (advanced devices measure changes in pupil diameter with sampling rate of above 1,000 samples per second), most past studies using pupil dilation have not investigated temporal changes. This led us, by using advanced statistical methods, to develop a novel analysis approach that provides detection as well as temporal characterization of cognitive processes. Our analysis detects differences in pupil size caused by different conditions and based on the time frames of the differences, can determine the location of a cognitive process in time. In a series of studies we have shown, by measuring changes in pupil size, evidence for increment and regulation of emotional processes, and the development of cognitive conflicts in cognitive control tasks.