The parent-child relationship includes a combination of behaviors, feelings, and expectations that are unique to a particular parent and a particular child. The relationship includes the full extent of a child's development. Of the many different relationships people form over the course of the life span, the relationship between parent and child is among the most important. The quality of the parent-child relationship is concerned by the parent's age, experience, and self-confidence; the stability of the parents' marriage; and the unique characteristics of the child compared with those of the parent. Parental self-confidence is an essential indicator of parental competence. Mothers who believe that they are effective parents are more competent than mothers who feel incompetent. Also, mothers who see themselves as effective also tend to believe their infants as less difficult to handle. Parental age and previous experience are also important. Older mothers tend to be more responsive to their infants than younger mothers. In addition, parents who have had previous experience with children, whether through younger siblings, career paths, or previous children, are oftentimes better able to cope with parenthood.