ACOUSTIC CHARACTERISTICS OF NATURALLY-OCCURRING CRIES OF INFANTS WITHCOLIC

Although infantile colic has long been defined by a perceived excessiv e amount of crying, acoustic attributes of the cry sound may also cont ribute to perceptions that this early social behavior is excessive or problematic. From an original sample of 76 infants (38 infants referre d to physicians for problematic crying, or ''colic,'' and 38 pair-matc hed comparison infants), 48 infants who produced naturally occurring c ry bouts both before and after an evening feeding were studied: 11 inf ants with Wessel's colic, 15 infants with non-Wessel's colic, and 22 c omparison infants. Standard and vociferous cry segments were selected from up to 2 min of tape-recorded crying for spectrum analysis. Vocife rous cry segments had a longer duration, a higher fundamental frequenc y, and a greater percentage of dysphonation than did standard segments . No differences between infant groups were found in cries before feed ing. After feeding, infants who were problematic criers, independent o f Wessel's criteria, showed a greater percentage of dysphonation in th e vociferous cry segment than did comparison infants. This finding res ulted from a decrease in dysphonation in the cries of comparison infan ts after feeding and an increase in those of infants with non-Wessel's colic. The dominant frequency also increased after feeding in the voc iferous cries of infants with Wessel's colic, resulting in these infan ts having higher-pitched cries after feeding than infants in the other 2 groups. Results indicate that infants who are perceived to have pro blematic crying have objectively different acoustic features in their cry sounds that are particularly aversive, and that complaints about e xcessive crying cannot be accounted for simply on the basis of reporti ng bias in overly concerned or emotionally labile parents.