Participant loss due to "fussiness" in infant visual paradigms: a review of the last 20 years.

One hundred and one published articles that used visual habituation or violation-of-expectation techniques with infants of 12 months or younger were surveyed. Information was compiled on the number of infants who failed to complete experimental procedures due to "fussiness" or other factors. Also noted for each experiment was whether or not infants as a group demonstrated differential responding to the test display. On average 13.7% (range 0-62%) of infants failed to complete these visual procedures as a result of fussiness. There was no correlation between experimental outcome and infant attrition due to fussiness or to any other factor. We thus found no evidence to suggest that differential exclusion rates systematically influence experimental outcomes. However, we urge researchers to provide operational definitions of "fussiness."