When parents cannot reach an agreement regarding child custody, most courts try to decide custody based upon an analysis of what arrangement is in the best interests of the child. While statutes and standards differ from state to state, a best interests determination is usually reached by reviewing parental wishes, the mental and physical health of the parents, any history of domestic abuse, review of the child's age and attachment to the parent that has been the primary caretaker, and the child's wishes depending upon the age of the child and the motivation for the preference.