Last week, I was in Montreal, Canada, looking to check into a hotel. A colleague was with me, using a map on his phone to navigate. He turned one way, then another, trying to determine the right direction. Meanwhile, I lifted my head, looked around, and immediately spotted the hotel sign glowing brightly down the road. When I tried to point it out, he asked me to wait – he hadn’t yet confirmed the correct direction on his phone. I laughed and said, “But I can see it.” He chuckled and admitted that sometimes, the technology isn’t all that helpful – or even necessary.
Hessels and his colleagues take a similar approach in their paper. As the first in a series of articles on the fundamentals of eye tracking, they begin with a simple yet crucial question for researchers new to the field: “Do you need an eye tracker for your study?”
The paper provides a framework to help researchers answer that question and situate their work within the broader field of science. It encourages scholars to ask – and equips them to answer – the following key questions:
- Am I studying eye movements themselves (e.g., where, when, or how gaze moves), or am I using gaze as a proxy for something else (e.g., does where someone look influence their purchasing decisions)?
- Is my research focused on testing existing ideas (hypothesis-driven research) or generating new ideas that can be tested later?
- How strong is the link between the eye movement data and the underlying theory?
What makes this article especially refreshing is that it’s grounded in foundational research, providing lab-based and real-world examples to guide the reader. These range from classic studies on reading, oculomotor control, and scene perception, to more applied research on eyewitness testimony, expertise, and educational design. Each example is carefully chosen and thoughtfully described to highlight different ways data and theory interact.
For instance, take Huey’s (1900) research on reading, which sought to describe the fixate-then-move sequence of eye movements. This work falls squarely in the idea-generating category of eye movement research. Hessels et al. take care not to oversimplify, noting that “Huey saw the description of research as a necessary step to understanding the reading process, and perhaps human cognition.” Their discussion illustrates how observational eye movement studies can inform theory just as much as theory can drive eye movement research.
They reinforce this latter point by shifting to oculomotor control research, where the theory-data relationship is particularly strong. Different models of oculomotor control are presented in a digestible way, showing how straightforward eye movement measures – like fixation duration – can be used to support or challenge competing theories.
Acknowledging that it can be tricky for both new and experienced researchers to pinpoint where their study falls on the data-theory spectrum, the authors provide practical guiding questions and a detailed breakdown of methodological approaches.
For those using eye tracking in an exploratory manner, they outline several essential considerations, such as:
Can the task be performed without making eye movements? Would performance suffer if eye movements were restricted? Do patterns of gaze behavior change based on certain factors (e.g., age, cultural background, expertise)? Concrete examples help researchers navigate these questions with clarity, illustrating how nuanced shifts in gaze behavior can provide insight into cognitive processing and attentional mechanisms.
Similarly, for those using eye tracking in a theory-driven study, they pose questions like: Is there a clear link between the theory and eye movement measures? If not, is an eye tracker really the best tool for the study? What theoretical assumptions underlie the interpretation of gaze patterns, and how might competing models influence data analysis? By integrating both theoretical and practical perspectives, Hessels et al. offer a comprehensive guide for researchers at any stage of their academic journey.
This article is an outstanding introduction to eye movement research, offering newcomers a strong foundation to build upon. As the first in a series on the fundamentals of eye tracking, it sets the tone for what’s to come. The expertise of lead author Roy Hessels and senior author Ignace Hooge shines through, and like true experts they present their material in an engaging, accessible style. Their work is not just informative but also thought-provoking, encouraging researchers to critically assess their methodological choices and the broader implications of their findings.
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Hessels, R.S., Nuthmann, A., Nyström, M., Andersson, R., Niehorster, D. C., Hooge, I. T. C. (2025). The fundamentals of eye tracking part 1: The link between theory and research question. Behav Res 57, 16. https://doi.org/10.3758/s13428-024-02544-8
