How eye movements and brain activity shape reading comprehension

Story and multimedia by Joey Garcia, University Communications and Marketing

Reading seems like a straightforward process. The eyes scan the words, and the brain turns them into meaning. But it's not always that simple. Readers regularly skip words, sometimes without realizing it. New research from USF shows how the brain still processes those skipped words using peripheral vision, even as the eyes move past them.

Elizabeth Schotter, associate professor and director of the USF Eye Movements and Cognition Lab, worked alongside first author and postdoctoral research scholar Sara Milligan on the study published in Psychophysiology.

"Our findings suggest that readers aren't simply guessing words; they rely on detailed visual and linguistic processing," Milligan said. "This supports the importance of learning letter-sound relationships and spelling rather than relying solely on contextual guessing strategies."

The study shows that reading happens through teamwork between the eyes and the brain, which work together to read quickly while still understanding the text. While the team's research addresses basic science questions, it lays the groundwork for new ways to address reading challenges and improve instruction.

COMBINING EYE TRACKING WITH EEG TECHNOLOGY

Eye movements during reading occur roughly every 250 milliseconds, and many processes must happen simultaneously under the hood to make comprehension possible. To track such movements, the team used an electroencephalogram (EEG) cap that measures brain waves, which requires careful setup to ensure accurate readings.

At the same time, they used a camera-based eye-tracking system to monitor participants' gaze as words appeared on the screen. This approach lets researchers link eye movements directly to real-time brain activity. Together, the tools revealed split-second choices about which words readers engaged with and the neural activity surrounding those moments.

"This study is unique because it allows participants to read naturally while simultaneously measuring eye movements and brain activity," Schotter said. "Many previous studies limited eye movements or relied on only one method. By combining both approaches, we can observe how real-time decisions during reading relate directly to brain activity."

The study included 55 participants, each of whom had a tracked reading session lasting approximately two hours. Participants silently read 180 sentences presented one at a time on a screen. In some cases, the researchers manipulated upcoming words to be expected, slightly altered or unexpected, allowing them to compare how the brain responded depending on whether a word was skipped or directly read. After finishing each sentence, participants pressed a button to continue.

"We are addressing two major issues: How people read and what separates skilled from less skilled readers," Schotter said. "Understanding these mechanisms can inform educational approaches and interventions. The second challenge is technical, since combining eye tracking with EEG required us to develop new tools and software. That work allows researchers to study reading in more realistic ways."

PROCESSING SKIPPED WORDS DURING READING

When the sessions concluded, the team gathered data from the brain-wave cap and the eye-tracking system. They matched the information to identify connections between what the eyes and the brain were doing while reading.

The study further shows that skipping a word does not mean it was ignored. Brain data demonstrated that readers often partially register skipped words in advance, and this processing can be deep enough to detect whether a word is expected or irregular. However, decisions to skip are made before full word recognition and integration are complete, meaning the brain operates on a fast, predictive system that prioritizes efficiency.

Now with a clearer understanding, the lab aims to explore how reading strategies change depending on goals, such as reading for comprehension versus skimming. Researchers also want to study individual differences, including why some people read faster or more efficiently, and how reading strategies and brain processing change across the lifespan.