The cries of infants and children are familiar to essentially all adults, and we all have our own common sense notions of the meanings of various cries at each age level. As is often the case, in the study of various aspects ofhuman behavior we often investigate what seems self­ evident to the general public. For example,if an infant cries, he or she needs atttention;if the cry is different than usual, he or she is sick; and when we areupsetby othermatters, children's crying can be very annoy­ ing. As a pediatric clinician often faced with discussing with parents their concerns or lack of them with respect to their children's crying, these usual commonsense interpretations were frequently inadequate. As this book illustrates, when we investigate such everyday behaviors as children's crying and adults' responses to crying, the nature of the problem becomes surprisingly complex. As a pediatrician working in the newborn nursery early in my career, I knew from pediatric textbooks and from nursery nurses, that newborn infants with high, piercing cries were often abnormal. In order to teach this interestingphenomenon to others and tounderstand under what circumstances it occurred, I found I needed to know what consti­ tuted a high-pitched cry or even a normal cry, for that matter, and how often this occurred with sick infants. Certainly I saw sick infants who did not have high-pitched cries, but I still wonderedif their cries were deviant in some other way.