People often seem to understand language before they have actually heard enough words to determine its structure. In everyday conversation, listeners react immediately, anticipate what others will say, and rarely wait for a sentence to finish. This raises the question of how the brain is able to keep up with such rapid communication.
In a new study, an international team of researchers, led by Associate Professor Chie Nakamura from the School of International Liberal Studies, Waseda University, Japan, investigated how listeners interpret structurally ambiguous sentences in real time using eye-tracking technology.
The team also included Professor Suzanne Flynn from the Massachusetts Institute of Technology, United States, Professor Yoichi Miyamoto from The University of Osaka, Japan, and Professor Noriaki Yusa from Miyagi Gakuin Women's University, Japan. Their findings have been published in the journal Frontiers in Language Sciences on March 04, 2026.
In this study, the researchers leveraged ambiguous sentences and the visual-world eye-tracking paradigm to observe how interpretation develops moment by moment during spoken comprehension. They found that listeners commit to one syntactic interpretation even while the sentence remains structurally ambiguous. Rather than passively waiting for grammatical information to unfold, listeners actively build sentence structure in real time.
"We often assume we understand a sentence only after hearing enough words to determine its structure. Our findings show that the brain actively builds sentence structure as the sentence unfolds, predicting how the sentence will continue before all the information is available," highlights Nakamura.
Using eye-tracking during spoken comprehension, the researchers found that listeners commit to one syntactic interpretation even when the sentence remains structurally ambiguous. The results reveal that listeners adopt a preferred syntactic structure prior to receiving explicit structural confirmation. By comparing English and Japanese and examining native English speakers and Japanese speakers learning English as a second language, the researchers found that predictive processing depends on language structure. English speakers rapidly favor one interpretation, whereas Japanese speakers show a different timing and pattern. Japanese L1 speakers who are L2 learners of English also adjust their predictive strategy to English rather than simply transferring their native-language processing. These results indicate that comprehension is proactive structure building, not passive decoding, and provide new insight into how the brain processes language and how bilinguals understand a second language.
The findings help explain why listening in a second language can feel difficult even when the words are known. Comprehension depends on predicting sentence structure in real time, and this prediction is tuned to each language. Learners therefore cannot rely only on vocabulary or translation; they must also learn how the language organizes sentences. According to Nakamura, "This has implications for language teaching, suggesting that language learning involves more than acquiring vocabulary. Exposure to natural sentence patterns and listening practice may help learners develop the real-time processing skills needed for successful comprehension."
Beyond language learning, the results are relevant to communication in noisy or fast-paced environments, such as classrooms, conversations, or online meetings. Because listeners rely on structural predictions, comprehension can break down when speech unfolds unexpectedly or too quickly.
The findings may also inform the development of speech recognition systems and language-learning technologies by encouraging models that anticipate likely sentence structures rather than processing words only after they occur.
