Master thesis: pupil size and response inhibition

This work focuses on how moment-to-moment fluctuations in arousal, indexed through pupil size, shape inhibitory control.

In my Master’s thesis, I investigated whether baseline pupil size prior to task onset predicts response inhibition performance in a stop-signal paradigm. The findings demonstrated that larger pretrial pupil sizes—reflecting elevated arousal—were associated with reduced inhibitory success and faster response execution. These results suggest that the cognitive state preceding an action plays a critical role in determining behavioral outcomes, with heightened arousal biasing individuals toward faster, more impulsive responding. 

Building on this work, I contributed to an extended research project examining the relationship between tonic norepinephrine (NE) activity and response inhibition using pupillometry as a non-invasive proxy. Across multiple experiments, we showed that pretrial pupil dynamics (both absolute size and rate of change) reliably predict fluctuations in task performance. Specifically, higher tonic arousal levels were linked to: • Faster go responses, • Reduced stopping success, • And nuanced effects on stopping speed itself.

These findings indicate that arousal-related neuromodulatory processes influence not only inhibitory control but also broader response dynamics, suggesting that the locus coeruleus–norepinephrine (LC-NE) system plays a domain-general role in regulating cognitive performance rather than a purely inhibition-specific one. 

Methodologically, this work combines eye-tracking, computational modeling of response inhibition (horse-race framework), and advanced statistical modeling to capture trial-by-trial variability in behavior. Conceptually, it contributes to a growing body of research emphasizing the importance of pretrial brain states and proactive control mechanisms in shaping cognition.

Overall, this research provides novel insights into how intrinsic fluctuations in arousal influence executive function, with potential implications for understanding clinical conditions characterized by impaired inhibitory control, such as ADHD and related disorders.