Tobii Scientific publications

Research and reports

Are you in the zone?

How pupil size can help us understand the ‘flow state’.

Resource Details

  • Written by

    Ieva Miseviciute

  • Read time

    2 min

Have you ever been engaged in an activity so intensely, to the point that you lose track of time and your surroundings? This is called the flow state or what we know as being in the zone. This mental state is characterized by complete task immersion, optimal focus, and pure enjoyment of the activity.

The research group from Erasmus University in Rotterdam, led by Dr. van den Linden and Dr. Bakker, endeavored to uncover the neurocognitive underpinnings of the flow state. The first author of the research study is a Ph.D. student Hairong Lu. 

One of the brain structures potentially involved in the flow state is the Locus Coeruleus- Norepinephrine system (LC-NE). The LC is a tiny nucleus in the brain stem and is the primary source of the neuromodulator norepinephrine (also known as noradrenaline) to most brain regions. LC-NE activity also directly modulates the level of arousal and focus. The optimal task engagement follows an inverted-U shape of arousal (see Yerkes – Dodson relationship).

Tobii Scientific publications
Yerkes-Dodson relationship between performance and arousal. Adopted from Aston-Jones and Cohen (2005).

The LC-NE system directly modulates alertness-related pupil dilation, and tracking changes in pupil size is a well-established indirect method to monitor LC-NE activity. Another way to indirectly monitor LC-NE activity is through EEG measurement of the P300. The P300 is the event-related potential regulated by attention and changing task demands representing cortical activity linked to LC-NE. The researchers in this study combined pupil dilation measurements with electroencephalography (EEG) recordings while the participants were engaged in the subjective flow state.

The study results showed that flow state and two indicators of LC-NE activity (pupil size and P300 amplitude) show the same inverted-U shape relationship with increasing subjective task difficulty.  The study also showed a positive linear relationship between psychological flow and pupil dilation – the pupil dilates more in the task in which an individual reports a higher feeling of flow.

These research findings illuminate how pupil dilation could be a nonintrusive way to capture the psychological flow state since this mental state cannot be interrupted in order to gather individual statements. Moreover, the study shows the involvement of LC-NE in the experience of flow state.


Lu, H., van der Linden, D. & Bakker, A.B. Changes in pupil dilation and P300 amplitude indicate the possible involvement of the locus coeruleus-norepinephrine (LC-NE) system in psychological flow. Sci Rep 13, 1908 (2023).

Cited publication

Aston-Jones, G. & Cohen, J. D. An integrative theory of locus coeruleus-norepinephrine function: Adaptive gain and optimal performance. Annu. Rev. Neurosci. 28, 403–450 (2005).

Read more

Interested in similar articles? Visit our scientific publication hub to see all our scientific publication highlights.

Resource Details

  • Written by

    Ieva Miseviciute

  • Read time

    2 min

    Resource type

    • Research and reports

    Tagged products

    • Eye trackers

    Tagged solutions

    • Scientific research


Related content

eye tracking

Power of the pupil

Eye tracking is a tool that uses eye movements to help researchers understand visual, perceptual, and cognitive processes. But there are some phenomena that are not definitively investigated by gaze behavior alone. Preference, emotion, and mental workload are examples of research that benefit from measures that extend the capability of eye tracking – like those of the pupil.

Learn more