ORIENTATION RESPONSES TO BIOLOGICAL ODORS IN THE HUMAN NEWBORN - INITIAL PATTERN AND POSTNATAL PLASTICITY

The initial pattern and development of odour preference was studied in infants simultaneously exposed to amniotic fluid (AF) and maternal la cteal secretion (L). Five groups of varying age (range: 1-5 days) and breast-feeding experience (range: 0-32 feeds) were studied. Before pos tnatal day 3, no evidence of differentiation of AF and L was apparent. After 3 days and 7-12 breast-feeding episodes, a significant preferen ce for L arised. The initial stage (days 1-3) may reflect fetal acquis ition of AF odour and sensory/motivational equivalence of AF and L odo urs. The second stage (days 4-5) may reflect the infants' perception o f change in milk quality and increasing experience with milk. This seq uential development attests to a high plasticity in the initial stage of human olfactory development.