What is distinct about infants' "colic" cries?

AIMS: To investigate (1) whether colic cries are acoustically distinct from pre-feed "hunger" cries; (2) the role of the acoustic properties of these cries versus their other properties in accounting for parents' concerns about colic.
DESIGN: From a community sample, infants were selected who met Wessel colic criteria for amounts of crying and whose mothers identified colic bouts. Using acoustic analyses, the most intense segments of nine colic bouts were compared with matched segments from pre-feed cries presumed to reflect hunger.
RESULTS: The colic cries did not have a higher pitch or proportion of dysphonation than the pre-feed cries. They did contain more frequent shorter utterances, but these resembled normal cries investigated in other studies. There is no evidence that colic cries have distinct acoustic features that are reproducible across samples and studies, which identify a discrete clinical condition, and which are identified accurately by parents.
CONCLUSIONS: The most reliable finding is that colic cries convey diffuse acoustic and audible information that a baby is highly aroused or distressed. Non-acoustic features, including the prolonged, hard to soothe, and unexplained nature of the cries may be specific to colic cries and more important for parents. These properties might reflect temperament-like dispositions.