Children’s inner speech begins to stabilise earlier than previously thought, study finds

Research from the University of Tsukuba reveals that a simple counting task can track the development of silent inner speech in children, suggesting stability arises around age five, a development that could reshape understanding of childhood self-regulation.

Researchers at the University of Tsukuba have found that a simple counting exercise may offer a window into how children develop inner speech, the silent inner narration people use to organise thought, guide behaviour and support self-control. In work published in Acta Psychologica, the team asked children aged three to six, along with adults, to count from one to five both out loud and in their heads, allowing the researchers to compare how steadily each person could repeat the task.

The key measure was how much counting time varied across repeated attempts. According to the study summary in PubMed and the journal report on ScienceDirect, silent counting became more consistent as children got older, with the youngest participants showing the greatest variation. Counting aloud did not follow the same age pattern, which suggests the change was not simply a matter of getting better at counting. The researchers said this points to a developmental shift in the mental process itself rather than in basic number skills.

The study also asked whether children believed it was possible to use words internally without speaking or moving their mouths or fingers. Adults were far more likely than children to say yes. Among the children, however, that explicit awareness did not line up neatly with performance on the task. As the researchers noted, that gap suggests children may already be using language privately before they can explain the experience in words.

The findings add to a broader body of psychological research that treats inner speech as an important part of cognitive development. Reviews on PubMed Central and specialist psychology resources have long described inner speech as emerging from earlier social or private speech, but have also noted how difficult it is to measure directly in young children. The Tsukuba team’s task offers a more practical approach, and their results indicate that a stable form of inner speech may begin to take shape around age five, earlier than some previous accounts had suggested.