Definition of mutism. : the condition of being unable to speak whether from physical, functional, or psychological cause.
Adolescents rushing to become adult have pushed the government reconsider the age of responsibility. Therefore, 21 is the age of responsibility taking account: decision making, impulse control and maturity. To begin with, the age of responsibility is defined by a persons decision making. Poor decisions at times lead teenagers to more dangerous/complicated situations.
In contract law a person who agrees to a transaction becomes liable for duties under the contract unless they are legally incompetent. A person under the age of 18 or 21 (depending on the jurisdiction) is not bound by the legal duty to perform the terms of a contract he signed and is not liable for breach of contract.