Objective The objective is to (1) analyse the logic of reasons given for non-nutritive thumbsucking and (2) find other reasons for thumbsucking.

Methods A critique of present explanations for thumbsucking is developed and an explanatory paradigm for thumbsucking is found by literature search.

Results (1) The critique of common reasons given for thumbsucking:

1. 1. Need to suck VS If it were a need to suck then infants would suck on any object to fulfill this need.

   2. It is normal behaviour VS It only occurs in other mammals when they are human reared and does not occur in societies where the infant has free access to the breast/nipple.

   3. It does no harm VS Thumbsuckers are more likely to develop facial malocclusions and dummy suckers are more likely to develop otitis media. Thumbsucking, a self fixation may also last into adulthood.

   4. It is learned behaviour VS Learned behaviour does not explain the emotional distress when the infant is denied access to the fixated object for sucking.

(2): The best explanation for thumbsucking is the behaviour recorded across the spectrum of mammals and is referred to as “teat preference” “teat specificity” “teat selection” “teat territoriality” and “nipple confusion”.

Conclusions The mammalian preference for selecting one teat for sucking is a genetically determined survival strategy to attach the newborn to the source of nutrition. Sucking is used to form an emotional relationship with the sucked object and thumbsucking is displacement onto a decoy.