Dr. David M. Levy, a child psychiatrist of New York City, concluded, after a series of clinical studies of children1 and experiments with animals,2 that babies suck their thumbs primarily because they do not get enough sucking from breast or bottle.
As a nurse in a Child Health Station of the Department of Health of the City of New York, I had a ready opportunity to test this conclusion. Furthermore, I was sufficiently well acquainted with the mothers who attended the station to be able to select those whose information was reliable. Even so it was necessary, after a preliminary study, to dismiss a number of informants because they were vague about changes in feeding schedules.
Only infants 7 to 8 months of age were selected, and data were collected concerning the feeding schedules followed during the first seven months. Fifteen known thumb suckers and fifteen known non
ROBERTS E. THUMB AND FINGER SUCKING IN RELATION TO FEEDING IN EARLY INFANCY. Am J Dis Child. 1944;68(1):7–8. doi:10.1001/archpedi.1944.02020070014003