Most explanations of the causes of stuttering will include at least threee possible causes, since no one knows for sure. Of these, the physiological (more precisely, neurological) cause is discussed as a probablility. However, some believe it's a learned behavior while others modify that slightly by adding the complnent of anxiety caused by overt criticism of stuttering during childhood.
It does appear that there may be some genetic factor since case studies suggest it runs in families, and produces certain focal abnormalities in persons who stutter