Selective Mutism

This clip from ABC News discusses selective mutism. Children with selective mutism are able to speak regularly when at home but are unable to do so at school or in unfamiliar situations.

The Galie family is documented; seven-year-old Morgan is a chatterbox at home, but does not speak in class. Morgan feels afraid and is unable to function socially, emotionally, and academically. In some situations, Morgan is able to respond but not able to ask questions.

What is the goal of Morgans therapy? What is contingency management and how is it used in therapy of children with selective mutism?