Ingestion, suckling, and the problem of identity: using criteria in the classification of ingestive behavior.

The data reported by Nizhnikov et al. [Newborn rats first suckling experience: taste differentiation and suckling plasticity (2002)] do not support the authors' claim that they shed light on suckling mechanisms. A number of accepted criteria for identifying suckling are discussed in this review. The ingestion of various fluids through a plastic tube by neonatal or other rats does not meet any of these criteria. Thus, while the data reported by Nizhnikov et al. [Newborn rats first suckling experience: taste differentiation and suckling plasticity (2002)] are of interest from the perspective of infant capabilities, they do not shed light on the determinants of actual nipple attachment or suckling as they may naturally occur.