A court reviewing a petition for amendment or replacement of a court-ordered parenting plan will employ the "child's best interest" standard in light of circumstances or changes in circumstances such as a parent's relocation, the presence or absence of child abuse in one or both parents' households, and health problems of a parent or the child. If the parents in a custody dispute request, many states allow children who are old enough to state an informed preference, to testify about their own preferences as to custody and parenting time, with their opinion taken into consideration by the court along with all other evidence relating to their best interest. The weight assigned by the court to a child's testimony will vary with factors such as the child's intellectual and psychological maturity, for which the child's age is often used as a proxy; the child's level of insight into his or her situation; and the credibility of the child's testimony as affected by factors ranging from the child's level of honesty to any undue influence on the child by either or both parents.