Parents should not worry when their pre-schoolers talk to themselves; in fact, they should encourage it, says Adam Winsler, an associate professor of psychology at George Mason University. His recent study published in Early Childhood Research Quarterly showed that 5-year-olds do better on motor tasks when they talk to themselves out loud (either spontaneously or when told to do so by an adult) than when they are silent.

"Young children often talk to themselves as they go about their daily activities, and parents and teachers shouldn’t think of this as weird or bad," says Winsler. "On the contrary, they should listen to the private speech of kids. It's a fantastic window into the minds of children."

In the study, "'Should I let them talk?': Private speech and task performance among preschool children with and without behavior problems," 78 percent of the children performed either the same or better on the performance task when speaking to themselves than when they were silent.

The study also showed that children with behavioral problems (such as those diagnosed with Attention Deficit Hyperactivity Disorder, or ADHD) tend to talk to themselves more often than children without signs of behavior problems.

"Given that kids with behavior concerns need more direction and control from adults, teachers may unnecessarily ask children to be quiet in classrooms out of fear that such speech coming from difficult-to-manage kids will lead to problem behavior," says Winsler. "Yet non-disruptive private speech would actually help these children as they develop. Therefore, teacher training and professional development efforts should suggest that teachers increase their tolerance level for this kind of private speech."

Winsler says that private speech is very common and perfectly normal among children between the ages of 2 and 5. As children begin talking to themselves, their communication skills with the outside world improve.

"This is when language comes inside," says Winsler. "As these two communication processes merge, children use private speech in the transition period. It's a critical period for children, and defines us as human beings."

Winsler also conducted the first-ever study looking at private speech in children with autism. He found that high-functioning autistic children talk to themselves often and in the same ways that non-autistic children do. Talking aloud also improved their performance on tasks.

"Children with autism have problems with their external social speech, so psychologists assumed that their private speech would also be impaired," says Winsler. "But this study shows that it is not the case—that autistic children use their private speech very effectively as a tool to help them with tasks."

The study, "Private Speech and Executive Functioning among High-Functioning Children with Autistic Spectrum Disorders," was just published in the Journal of Autism and Developmental Disabilities.