Abstract
The pupillary response is influenced by both cognitive processes, such as arousal and attention, and non-cognitive processes, such as luminance. To study physiological markers of cognitive processing, researchers use luminance-matched stimuli to minimize the influence of non-cognitive factors on pupil response changes. As such, extant pupillometry research may be confounded by task-structure which limits its applicability to other contexts. To investigate whether commonly defined phasic (peak amplitude, peak latency) and tonic pupil (baseline) features generalize across contexts, we leveraged a unique longitudinal pupillometry data set that involved performance of mental arithmetic (MA), visual working memory (VWM), and psychomotor vigilance (PVT) tasks. Participants (N=30) completed these tasks on 8 separate sessions over the course of 16 weeks, allowing us to address a number of questions about the task-dependence of pupil features: (1) which pupil features are consistent across tasks? and (2) which pupil features show reliable relationships to behavior (response time (RT)) within and/or across tasks? Results showed that mean baseline pupil diameter was consistent across the three tasks, whereas task-evoked phasic features (peak amplitude and latency) were not consistent (i.e., they were highly task-specific). However, despite being uncorrelated from task-to-task, phasic features showed a strong positive relationship with behavioral RT’s both within and across the three tasks. Peak latency, in particular, tracked RT very closely for all three tasks: MA: mean RT 3.18s & mean latency 5.75s; VWM: RT 0.70s & latency 3.23s; PVT: RT 0.41s & latency 2.31s. Baseline pupil diameter was also significantly associated with mean RT such that higher baseline was predictive of faster responses. These findings suggest that peak amplitude and latency, while task-specific, reflect a common pupil-linked decision process, while baseline reflects more stable pupil-linked arousal processes that also contribute to performance.