By Emily Willingham HealthDay Reporter FRIDAY, Oct. 23, 2015 (HealthDay News) -- It's a little-known anxiety disorder that renders one in every 150 children speechless in certain situations. Called "selective mutism," the inability to speak is not a choice for these youngsters, experts say. "It's best described as a phobia of talking," said Alison Wintgens, an advisor to the Royal College of Speech and Language Therapists in England, and author of a resource manual on the condition.