IMPRINTING 

The behavioral process that takes place during a sensitive period in the early hours of life during which the baby’s evolutionary biology enables it to orally fixate to a stimulus feature (normally the mother’s nipple and the surrounding suckling area) and learn its tactile characteristics.

One teat preference is predominant across the mammalian spectrum and is co-evolutionary with the process of imprinting as a genetically determined strategy for survival (compare displacement leading to fixation on a dummy / thumb / decoy).

Mobbs E  1989 Breastfeeding Review  1 :39