Ethan Kutlu, assistant professor of communication sciences and disorders in the College of Liberal Arts and Sciences and CSSI researcher affiliate, recently published a study tracking how school-aged children categorize speech sounds. It changes the way that researchers and parents can track progress and enrich language development. 

Speech categorization, such as distinguishing between the sounds of “p” and “b,” is important for processing spoken language and learning to read, and it traditionally has been thought to develop very early in a child’s life.

However, Kutlu’s research supports new evidence that speech categorization continues to evolve beyond the first year of life, extending into elementary school years and becoming more refined.

“One of the most famous theories in language science, particularly in speech sciences, is the idea that infants must learn the sounds of their first languages during the first year of life,” he said. “This fast-learning period was expected to help with language development. The faster you learn about the sounds, the faster you start learning words and build sentences. However, language acquisition is an ongoing process.”

Kutlu’s research team tracked 225 children in first through third grades over four years, extending to fourth through sixth grades. They studied how well the children categorized speech and how consistently they did so—the latter has been largely overlooked in previous studies. 

The children listened to two similar-sounding words and indicated what they heard using a new continuous scale rather than a traditional “pick one” forced-choice test. For example, children were shown a touchscreen line with “peach” on one end and “beach” on the other. Instead of choosing one word that they heard, they tapped anywhere along the line to indicate whether the sound was closer to “peach,” closer to “beach,” or somewhere in between.

As children grew older, they not only became more consistent with their selections, but also separated similar-sounding words more sharply, showing that they paid greater attention to the fine details of speech sounds.

The study noted that increased consistency as children age may be due to developmental changes from growing social networks and exposure to a variety of speakers and more complex language. “One of the most important take-home messages we can provide is that parents should not only consider the first couple of years as the critical window to language acquisition but also should continue to support their children’s language development when schooling begins,” Kutlu said. 

“Having rich linguistic environments is key to increasing consistency in speech categorization.”

The study titled, “Longitudinal Changes in the Structure of Speech Categorization Across School Age Years: Children Become More Gradient and More Consistent,” was published in Developmental Science. The other study authors included two researchers from the Department of Psychological and Brain Sciences: Hyoju Kim, postdoctoral research scholar, and Bob McMurray, professor.

The study was part of the Growing Words Project, a multi-million-dollar initiative led by McMurray, which focused on examining elementary-aged children's language abilities in Iowa City and Cedar Rapids, Iowa.

“Having access to this longitudinal sample, thanks to Dr. Bob McMurray’s NIH funding, played an integral role in exploring such impactful outcomes,” Kutlu said.

Last year, Kutlu participated in CSSI’s Grant Writing Residency Program and completed a grant proposal to further support his research on language development. He submitted the grant to NIH this past fall. 

“While I was working on that grant, I wrote this manuscript,” he said. “So, the space CSSI provided was integral in helping me shape my ideas.”