Tobii : How to choose the right eye tracker, without having price be the only guide

With a portfolio ranging from a few thousand dollars/Euros/pounds and up, many aspiring eye tracking researchers first ask, 'How much do your eye trackers cost?' While the budget of the hardware is important, it shouldn't be the primary consideration. Investing in a non-optimal eye tracker could end up costing you later, in wasted time, resources, and grant funding.

Now, let's walk through the common questions to consider when budgeting for a new eye tracking system so you choose the right eye tracker the first time.

1. What types of stimuli are you showing your participants?

2. What kind of participants are you testing?

3. What kind of environment are they in?

4. Which metrics are the most important to measure your construct of interest?

What type of stimuli are you showing your participants?

The stimuli and paradigm you use for your study will determine whether you need a screen based or wearable eye tracker. If you are presenting your stimuli on a computer monitor, we would mostly likely recommend a screen-based system. For example, if you are presenting images, videos, web sites, or blocks of text, a screen-based system would work well.

If your stimuli are not presented on a computer, there are two options:
1) setting up a screen-based system in a non-standard configuration, or
2) using our wearable Tobii Pro Glasses 3.

There are also some gray areas where either eye tracker type could work, depending on your specific research question. For example, let's say you're interested in measuring where participants look as they use a mobile phone. If you are most interested in assessing the usability or user interface design of the operating system, you may use our Mobile Testing Accessory. This product will hold both the screen-based eye tracker and mobile phone in a position to get accurate, precise visual data during use.

Alternatively, if you are most interested in how people use their phones more naturalistically while engaging in a second task, like driving, then our Tobii Pro Glasses 3 wearable system is a better choice. This allows you to measure attention to the mobile device, as well as the entire environment, like the roadway and cockpit of the car.

Of course, if you have a unique application or other considerations, our team can help walk through your paradigm and protocol to determine the right product fit for your needs.

What is your population? (e.g., infant, child, aging, clinical, non-human primate)​

Fortunately, our Pro Fusion and Pro Spectrum screen-based systems are highly tolerant of head and body movement - though that can't be said for all other eye trackers on the market. Dual cameras​ in Tobii systems mean no head restraint or chin rests are required to obtain good quality data. This is critical for studies with infant and child populations, and allows non-human primates to engage naturally without restraints.

Tobii systems will also work well with individuals across the lifespan, from a few months of age and up. Our Tobii Pro Spectrum system can even be calibrated and used in a monocular mode, if needed.

We have also done extensive testing with our screen-based systems to ensure robustness across eye color, eye shape, vision correction status, and ethnicities in different geographic regions. This means you can collect a diverse sample of participants and still retain high data quality. Read more about our quality data metrics.

Additionally, our wearable Tobii Pro Glasses 3 system can be used to capture eye movements of children as young as 5 years old. It is possible even younger children could wear the Pro Glasses 3, but we have not done extensive testing with this age group. Want to be the first? Let's talk!

Where will you be collecting data: Lab-based research, field-based testing, or both?

Our hardware can be used in both a traditional laboratory setting, or anywhere else. The Tobii Pro Spectrum is our all-in-one hardware with a built in 24' monitor. It comes in a wheeled case weighing about 50 lb/22 kg, so it can be your in-lab eye tracker or brought into the field. I have checked the Pro Spectrum as luggage on a flight and carried it in the trunk of my Toyota Prius. A colleague of mine regularly wheeled the Pro Spectrum onto the New York City subway system, so anything is possible!

Alternatively, the Tobii Pro Fusion comes in a padded, zippered case and plugs into a laptop using an USB-C adaptor, meaning set up fast and easy. While you can leave it attached to a lab PC, this hardware is small and portable, fitting in a carryon bag as under seat luggage on an airplane or checked in a suitcase.

For a wearable​ option, the Tobii Pro Glasses 3 comes in a lightweight padded case with a carrying strap. Use a tablet to connect to the recording unit and collect data, and you have the perfect kit to take into the field. I have also securely traveled with this in a both carry-on and checked suitcase. Just make sure the lithium-ion batteries go in the cabin with you - not in a checked bag!

In short, you can use Tobii Pro systems to collect data in university labs, schools, hospitals, community centers, or even from people in their homes. This also means our eye trackers are great for collaboration and sharing, if you're working on cross-disciplinary projects.

What type of eye movements do you want to study? (e.g., fixations, saccades, smooth pursuit)

Tobii Pro offers a range of eye trackers that vary in sampling rate, from 50 to 1200 Hz. The sampling rate frequency (e.g., temporal resolution or camera frequency) refers to the number of data points you will get per second, which ultimately defines what type of eye movements you can accurately measure. The higher the sampling rate, the more precise the measurement of true eye movement onset and offset (this is a pretty important point to consider. Discover more about eye tracker sampling frequency. However, a higher temporal resolution also comes at a cost, typically with faster (read: more expensive) cameras, parts, and ultimately more data to store. Not every research question needs a Spectrum 1200 Hz system to answer it!For dependent variables, many people use metrics of fixation, which is a period of relative stability of eye movement, usually accompanied by attention. Conversely, some people want to analyze saccades, which are the eye movements that shift foveal attention from point A to B. Using these metrics would necessitate different hardware. For some simple, fixation-based studies, our 60 Hz eye trackers may be sufficiently fast enough to measure attention to a simple stimulus. However, if you are interested in using saccadic eye movements as a dependent variable, you will need a faster system with speeds of at least 250 Hz and up to accurately capture the precise onset and offset of the eye movement. Learn more about fixations & saccades.

If you are interested in using the estimate of pupil size as metric, then consider these questions. Are you using simple percentage change in pupil diameter from baseline as a proxy for emotional arousal, cognitive load, or fatigue? A lower sampling rate system (e.g., 60 Hz) could work. Or do you need to understand dynamics, like the rate of pupillary change? If so, we'd recommend the Spectrum 300 and up. Finally, some of the hardware differences come into play, like number of cameras, since two camera systems are more stable than single camera systems across Z-distance for measuring pupil diameter. Our Pro Fusion and Pro Spectrum are both dual camera systems, which work to reduce z-distance measurement error for pupil diameter estimates.

The bottom line is the higher the sampling frequency, the better your ability to estimate the true path of the eye when it moves. You will have more certainty about where the eye movement starts and ends, making your research conclusions clearer.

Conclusion: Striking the right balance between price and features comes from letting your research question, paradigms, and dependent variables be the main influencers on the hardware choice. Hopefully these questions have provided some guidance on choosing the best hardware solution for your research.

Applying for funding to purchase your dream eye tracker? We can help! If you need customized assistance with your grant applications, our Funding Support Services provide complimentary support to researchers like you. Fill out a short interest form and one of our expert Research Scientists will reach out to guide you through the process.

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