Beyond one viewpoint: Synchronized research through Tobii Pro Glasses 3

Tobii Pro Glasses 3 are well-known for their accuracy and ease of use in wearable eye tracking research. Widley used by leading academic institutions and enterprises, they support a broad range of applications.

Occasionally there are requests for use cases that go beyond the standard applications, with synchronization of multiple glasses becoming an area of increased interest. Some users already leverage the unique abilities the Tobii Pro Glasses 3 offer to synchronize multiple eye trackers as well as other devices from our partners for multimodal research, ranging from EEG to Motion Capture devices.

Synchronisation capabilities further expand what researchers can accomplish, especially in studies that involve group interactions or shared activities. In this blog, we’ll provide an overview of how synchronization works and how it supports a variety of research areas.

Why synchronize multiple eye tracking glasses?

When several participants wear Tobii Pro Glasses 3 at the same time, their combined gaze data can show how individuals coordinate, communicate, and respond in shared tasks. Observing synchronized perspectives during group discussions or team-based challenges reveals patterns that may be missed in single-person recordings. It greatly reduces the number of recording sessions needed to capture behaviour from different perspectives.

Synchronization methods

There are several ways to synchronize multiple pairs of Tobii Pro Glasses 3, each with its own advantages:

• Separate Host Devices Setup: Connect each pair of Tobii Pro Glasses 3 to a separate device, such as a laptop or tablet. This method is straightforward but requires multiple devices and a more manual sync post-hoc, which is suitable if high synchronisation accuracy is not required.

• Router-Based Setup: Use a router to connect all Tobii Pro Glasses 3 units to a single host device. This centralizes control but may result in slight delays. A wireless connection or the build-in Ethernet port on the Recording Unit can be used to minimise potential wireless interference.

TTL Cable-Based Connection: Tobii Pro Glasses 3 feature a dedicated TTL synchronisation port on the Recording Unit. This type of parallel port remains one of the most common and robust techniques for synchronizing different recording devices. Designate one Tobii Pro Glasses 3 unit as the master to send signals directly to other units. Any other system that accepts a TTL input or has its own output can also use the same port to send or receive signals. This is easy to set up and ensures high accuracy. It does require cables between devices and may therefore not be suitable for situations where full mobility is needed.

• Custom Microcontroller Setup: Using a microcontroller to send precise signals through the TTL or Ethernet port gives more flexibility and can also allow wireless synchronisation. This approach requires some familiarity with hardware connections and custom development, but it offers precise timing when every millisecond matters.

• API-Based Integration: A custom software solution can use the
  Tobii Pro Glasses 3 API to manage multiple pairs of Tobii Pro Glasses 3. It can be used to send simple event triggers or to control simultaneous recording. Physical wiring can be eliminated, and the researcher gains full flexibility to control data collection and timestamps in one place. Several partner solutions designed for synchronization are built on Tobii’s API and are compatible with the Tobii Pro Glasses 3 for turnkey solutions.

Tobii Pro Glasses 3 unique synchronization capabilities

Although most of the above methods are suitable for many different projects, the integrated TTL port in Tobii Pro Glasses 3 can provide a unique extra level of timing accuracy. By working at the hardware level, it aligns data streams down to the millisecond. Researchers studying fast-paced tasks, fine-grained social cues, or neurological processes often require this level of accuracy.

TTL triggers are also highly robust and reliable, even in complex research environments with multiple systems running simultaneously. They reduce the risk of desynchronisation caused by latency or drift in systems, giving researchers confidence in the integrity of their data. It makes it easier to combine eye tracking with other data sources such as motion capture systems or biometric sensors such as EEG. This enables a deeper understanding of the relationship between visual attention and emotional or cognitive responses.

Multi-user research use cases

Many studies benefit from aligning data across several units of Tobii Pro Glasses 3. Each synchronized recording provides a window into how multiple individuals see and respond to the same moments, tasks, or spaces. Below are various areas where this technique offers valuable insights.

Group discussions and social exchanges

When two people or a group gather for a discussion, meeting, or teamwork exercise, synchronized glasses capture every glance. What captures the group’s attention moment by moment? Is gaze aligned across participants, or does it vary and is it driven by certain social cues? Studying these patterns can help to understand influence, engagement, or subtle social signals and optimise teamwork or training.

Sports performance

Coaches and sports scientists can equip multiple athletes (or fans!) with Tobii Pro Glasses 3 during training sessions or live events. Synchronized data reveals how players track the ball, coordinate with teammates, or monitor opponents. This information can be used to adjust strategy, personalise drills, and improve team communication.

Real-world navigation

Many eye tracking researchers are interested in how individuals move through large public spaces such as airports, shops, or museums. With synchronized eyewear, it becomes clearer how participants in a group, such as a family, chose directions, react to signage, or interact with each other or strangers along the way. Combined observations can uncover shared decision-making processes that might be missed in single-user recordings.

User experience and interface testing

In situations where two or more people are using a product together - whether it’s software, a website, or a piece of physical equipment - simultaneous recordings show overlapping or diverging points of focus. These moments help to highlight design pitfalls and opportunities for revision in situations where interactions don’t depend on a single user.

Collaborative learning

In an educational setting, synchronized eyewear can capture how groups of students share materials or guide each other through a problem. Who is consistently leading the group? Where do they focus, and what is commonly missed? These observations can help refine teaching methods and uncover group dynamics.

Human factors and ergonomics

Researchers studying work environments -whether in industrial facilities, offices, or laboratories — can use synchronized eye tracking glasses to see how multiple individuals collaborate, handle equipment or coordinate under different conditions. It becomes easier to spot design flaws in tools or layouts, identify safety risks, and propose adjustments that make tasks or procedures smoother or safer.

Relationship dynamics

Tobii Pro Glasses 3 also supports research into how relationships shape behavior. In parent-child studies, for instance, do parents focus on guiding the child, or are they distracted by other elements in the environment? In cooperative and competitive tasks, do close colleagues share a more consistent gaze pattern compared to strangers? Or does gaze differ between people with different levels of experience?

Merging eye tracking with biometric data

By combining synchronized eye tracking with inputs like heart rate, galvanic skin response, or EEG, researchers can look deeper into how attention links to emotional or mental states. Whether examining stress levels in healthcare scenarios or alertness in a high-stakes workplace, the addition of physiological measurements clarifies how individuals react in real time. Eye tracking itself can be used as a reliable indicator of stress, fatigue or workload in combination with algorithms designed to detect this
(Hu et al., 2024; Qian et al., 2024; Wu et al., 2024).

Training and development

Synchronizing multiple Tobii Pro Glasses 3 units during training sessions — military drills, sports practices, or emergency simulations — provides a clear record of where each participant looks at crucial moments. This helps identify effective strategies as well as areas that need improvement. Coaches, instructors, or supervisors can then fine-tune exercises to encourage better coordination, decision-making, or situational awareness.

Bringing it all together

The exact choice of synchronization method depends on project goals, technical requirements, and how critical timing precision is. Tobii can help you make the right decisions based on your research needs.

Router-based and API-driven approaches are often sufficient where millisecond accuracy is not required. However, the TTL port offers hardware-level alignment for research where every millisecond counts and is a unique feature of the Tobii Pro Glasses 3.

Researchers who need to collect data from multiple users will appreciate how Tobii Pro Glasses 3 simplify the process. Combining reliable tracking with robust synchronization capabilities, it supports a wide range of studies where coordinated attention and timing truly matter.

References

Hu, Y., Shen, H., Pan, H., & Wei, W. (2024). Fatigue Detection of Air Traffic Controllers Through Their Eye Movements. Aerospace, 11(12), 981.

Qian, C., Liu, S., Wang, Y., Ji, K., & Wanyan, X. (2024). A stress classification model based on physiological features in aviation operational tasks. In X. Kong & X. Wang (Hrsg.), Third International Conference on Intelligent Mechanical and Human-Computer Interaction Technology (IHCIT 2024) (S. 63). SPIE.

Wu, Y., Zhang, Y., & Zheng, B. (2024). Workload Assessment of Operators: Correlation Between NASA-TLX and Pupillary Responses. Applied Sciences, 14(24), 11975.