Stuttering is a disorder in which certain sounds, syllables, or words are repeated or prolonged, disrupting the normal flow of speech. Symptoms are generally worse in stressful situations such as talking in public or on the telephone, while talking or singing in unison may temporarily alleviate symptoms, a phenomenon known as the choral effect. Stuttering usually develops in young children as they are learning to speak and may occur in 2% to 5% of children at some stage. In the United States, approximately 3 million people or 1% of the adult population stutter. Usual treatment for stuttering includes various behavioral vocal techniques to assist speakers with generating difficult words or sounds and with actively monitoring their own speech.