Executive function and verbal self-regulation in childhood: Developmental linkages between partially internalized private speech and cognitive flexibility

• The development of executive function in childhood may be connected to the self-regulatory function of language.
• The children were able to flexibly change the rule continuously when they were 6 or 7 years of age.
• The results indicated increased internalization of verbal self-regulation with increase in age.
• The children use of partially internalized private speech was positively associated with executive task performance.

Recent studies have noted that executive function and the use of self-regulatory private speech are related in childhood, and proposed that the critical leap that occurs in the development of executive function between the ages of three and six years may be due to the onset of language-based self-regulatory functions at this age. This research explored the relationship between executive function and private speech in a cross-sectional study of 81 children between four and seven years of age. The children performed an executive function task, the Dimensional Change Card Sort (DCCS), and children's use of private speech was observed during a categorization task. The results indicated that, after controlling for children's age, gender, verbal abilities, and fluid reasoning, children's use of partially internalized private speech during the categorization task was significantly related to the number of phases successfully passed on the DCCS task, which required them to switch between card sorting rules. Children who used more partially internalized private speech were more likely to pass the most challenging phase of the DCCS task that assesses the ability to flexibly use different sorting rules according to a higher-order rule. We discuss the role of verbal mediation in the development of cognitive flexibility and its implications for the design of intervention programs for children who possess deficits of executive function.