Understanding cognitive load with Tobii eye tracking

Eye tracking opens a new window into human behavior, whether you're exploring attention, decision-making, or interaction, it provides powerful insights that help you understand how people engage with the world around them. 

What is cognitive load? 

Cognitive load is a measure of how much mental effort someone is using at a given time. Understanding it adds a new layer to eye tracking, or can be used as a stand-alone measure, showing not just where people look but how hard their brain is working. It can highlight confusion or mental stress during navigation, pressure points in usability tests, or decision-heavy moments in sports and professional training. 

Bringing cognitive load into Tobii workflows 

We’ve been working with SOMAREALITY’s Aware platform to integrate cognitive load insights into existing Tobii workflows. This overview explains how cognitive load is measured, how it’s applied with Tobii Glasses, and the value it brings to our customers and partners. 

Why cognitive load matters 

Working memory has limited capacity. When a task demands more than it can handle, performance drops.  

Research shows an inverted-U relationship between workload and performance: low load leads to boredom and drowsiness, optimal load produces peak performance, and high load causes errors, stress, and fatigue.  

Both extremes are risky. Underload reduces attention, especially in monitoring tasks or driving and flying or operating machinery. Overload increases mistakes and can cause chronic stress. Maintaining optimal cognitive load is critical for efficiency and safety. 

Eye tracking and cognitive load 

Traditionally, cognitive load has been measured through self-reports, performance metrics, or EEG. These methods are often intrusive or retrospective. Eye tracking offers a natural, real-time, and objective alternative. 

Key indicators include pupil diameter, blink dynamics, fixation patterns, and PERCLOS (percentage of eye closure). These signals can be used individually or together to track workload continuously in real-world environments. SOMAREALITY uses pupil diameter and compensates for light changes using scene camera analysis. 

SOMAREALITY’s Aware platform 

The SOMA Aware platform processes gaze and pupil data into so called biomarkers, currently focused on cognitive load normalized as mental effort over time. Future updates will include extended gaze metrics and a Conscious Perception Index. 

Outputs are available as CSV, video overlays, or in real time via Unity SDK. SOMA’s models are empirical and transparent, validated across aviation, medical training, and sports. 

Real-world applications 

Cognitive load has shown strong correlation with high-effort moments in driving, wayfinding, shopping, and sports.

• Driving: Spikes during lane changes and complex junctions.

• Wayfinding: Two participants navigating an airport showed spikes at the same confusing junction, confirmed by interviews.

• Usability and shopping: Peaks aligned with decision overload or confusing layouts.

• Sports: Spikes during critical decision moments.

Workflow for Tobii Pro Glasses 3 

Since Tobii Pro Lab doesn’t natively import third-party metrics, we developed a workflow using SOMA Aware’s CSV outputs. These are injected into Tobii Pro Glasses 3 data (using a small experimental application we created), replacing pupil data with cognitive load values. Analysts can then inspect and compare workload levels directly in Tobii Pro Lab. This workflow currently applies to Tobii Pro Glasses 3 recordings. If you are currently using Tobii Pro Glasses 2 check out our upgrade offer.

Value for customers and partners 

Cognitive load measurement adds value across training, safety, product design, navigation, sports, and healthcare. It helps adapt difficulty, monitor fatigue, assess operators, and identify decision chokepoints or when cognitive load peaks happen. 

Our partnership with SOMAREALITY strengthens Tobii’s offering by combining eye tracking with cognitive metrics. It helps our customers act on mental effort data using tools they already know. 

Next steps 

SOMAREALITY will present their solution in an upcoming webinar. For Tobii Glasses X, we’re exploring new approaches, including direct support in Glasses Explore. Meanwhile, our workflow for Tobii Pro Glasses 3 already demonstrates how Tobii and partner technologies can deliver immediate value.