UC Davis

Interval timing, a subcategory of time perception, is central to healthy cognitive functioning in everyday life. Findings have emerged highlighting a critical role of the motor system in supporting timing functions. Evidence for its importance stems from both neural and behavioral data; timing tasks are shown to activate motor brain regions such as the supplementary motor area, even when the tasks do not require overt motor responses. On the other hand, behavioral studies have shown that incorporating movement into timing tasks leads to changes in timing precision and accuracy, depending on the manipulation. Here, we examined the role of movement in time perception across three studies. Our first study was driven by prior findings that movements covering longer distances are perceived as lasting longer than movements covering shorter distances. We tested whether restricting arm movement via an external manipulation (i.e., a viscous movement environment) would lead to the same effect. As viscosity increased, perceived time was shortened, supporting our hypothesis. This study also highlighted that movement parameters do not need to be self-modulated to induce movement-related distortions. Our second study was motivated by a gap in knowledge surrounding movementtiming relationships: while existing studies had demonstrated that adding movement to timing tasks exerted changes to performance, the process by which participants judged the duration of their own movements was unknown. We compared accuracy and precision performance between three interval timing conditions: auditory, movement, and combined. The novel findings from this study were that movement intervals were underestimated compared to auditory intervals, and importantly, that timing accuracy was highest when these two signals were combined. Finally, we investigated the role of movement in timing for adults with ADHD. Studies of timing in this population are relatively uncommon and yield heterogeneous results, yet it is a topic of interest due to consistent patient reports of experiencing difficulty with time management. Our research previously found a beneficial effect of movement on timing precision in a sample of healthy adults, and here, we tested whether this would be the case for participants with ADHD. Surprisingly, a movement-related improvement in timing was not found for either the ADHD or control group. We suggest this may be due to the within-subjects manipulation and block design of the study, where participants experienced interleaved blocks of movement and non-movement trials. This contrasts with our prior study in which participants were assigned to a movement or non-movement group, and the observed benefit may have been dependent on the continuous exposure to the movement condition. Additionally, our sample size was relatively small, and potential differences may require more data to uncover. However, a notable finding was that participants with ADHD significantly underestimated time intervals compared to controls, which had not been previously established in the duration range that we tested. In summary, our studies addressed novel research questions about the qualities of movement that affect timing, how movements are timed in isolation and combined with concurrent sensory signals, and how movements interact with timing in adult ADHD. These advancements pave the way for further research on the nuances of movement-timing relationships, and how they influence human cognition on a broader scale.