In Japan’s bustling test prep culture, where every comma and clause can feel like a stepping stone to university, students learning English as a foreign language have long been told one thing: more complex grammar equals higher scores.

But what if that advice has been wrong all along?

A study from Kobe University, led by linguist Yasuda Sachiko, finds that students who write with clarity and conviction fare better than those who simply string together grammatically ornate phrases. The results, published in Assessing Writing, call into question how English writing is taught, evaluated, and understood in non-native settings.

Stronger arguments, not longer sentences

Essay writing has long served as a standard way to assess progress in English as a foreign language. In Japan especially, students pour hours into mastering elaborate grammatical forms, believing they are the golden ticket to high test scores. Yasuda, however, wasn’t convinced.

“Based on my experience of teaching academic writing to students at various levels in Japan,” she said, “I believe that linguistically complex texts do not always result in better writing.”

To test her hunch, she conducted an experiment with over 100 Japanese high school students. She asked them to write short essays and then analyzed two key elements: the structural complexity of the grammar and the complexity of the ideas expressed. She also looked at how well the essays were scored according to official rubrics.

Her results surprised even her.

“Interestingly, low scoring essays showed the highest level of complexity in finite adverbial dependent clauses,” Yasuda wrote in her paper. That means the students using the most grammatically intricate structures weren’t necessarily doing better.

The results flip conventional wisdom on its head. Even online, where overwhelmed students might search for shortcuts like “write my essay for me,” the real answer may be much simpler: focus on making a clear, reasoned point, not on cramming in as many advanced grammar structures as possible.

That’s because what did set high-scoring essays apart was the strength and clarity of the arguments. Lexical diversity—using a wide range of words—also factored in higher scores, as did noun modification and the number and soundness of arguments. In short, students who could express complex thoughts in varied, meaningful ways fared better, even if their grammar was simpler.

“Simply having complex sentence structures does not necessarily lead to a better essay,” Yasuda concluded.

Implications for teaching and testing

These findings carry weight far beyond the classroom. If grammar-heavy essays aren’t earning top marks, why do so many scoring rubrics in Japan (and likely elsewhere) emphasize them?

“Current rubrics for writing questions on language tests instruct test-takers to ‘use complex grammar appropriately’ or ‘a variety of complex structures,’” Yasuda noted. “However, since sentence complexity does not significantly affect overall essay quality, it may be more appropriate to use terms such as ‘contextually appropriate grammar’ or ‘genre-appropriate grammar.’”

In other words, grammar still matters—but only when it serves the writer’s intent and supports the message. Yasuda wants test designers to shift their focus to whether students can make meaningful points, not just bend language into contorted shapes.

And then there’s the so-called “washback effect”—how the nature of tests influences the way teachers teach and students learn. Yasuda sees this as a key part of her mission.

“I am committed to using the results of this study for practical applications,” she said, “such as refining assessment criteria for evaluating students’ writing, developing tasks and materials to improve their writing skills, and identifying the key knowledge that teachers need to help students become better writers.”

In a world where English has become a global tool for connection, the stakes are high. Being able to communicate ideas clearly—and persuasively—is more than a test skill. It’s a life skill.

“The ability to write in English has become increasingly important in the 21st century,” Yasuda said, “as it is a crucial medium that allows us to connect with others around the world.”

Her findings serve as a reminder: sometimes, less (grammar) really is more—especially when it helps students find their voice.