FACIAL AND AUTONOMIC RESPONSES TO BIOLOGICAL AND ARTIFICIAL OLFACTORYSTIMULI IN HUMAN NEONATES - REEXAMINING EARLY HEDONIC DISCRIMINATION OF ODORS

Responses of awake and asleep 3-day-old human neonates were recorded t o the presentation of artificial (vanillin, butyric acid, formula milk s) and biological (breast milk, amniotic fluid) odorants matched on su bjective intensity and trigeminal dimensions. The responses included b ehavioral (facial and oral movements) and autonomic (respiration, diff erential skin temperature) measures. The neonates reacted with signifi cant facial and respiratory changes to low concentrations of olfactory stimuli during the various behavioral states. The analysis of olfacto -facial configurations revealed that behavioral markers of disgust (no se wrinkling, upper lip raising) discriminated between some odors judg ed as being pleasant and unpleasant by adult raters (vanillin vs. buty ric acid). However, although some early predisposition to process the affective significance of stimuli may be suggested, no convincing evid ence was obtained that neonates discriminated the hedonic valence of o dors within the same perceptual space as adults. Finally, neonates evi nced a differential pattern of respiratory responding to the presentat ion of milk odors according to the mode of feeding (breast vs. bottle feeding), suggesting that early olfactory discrimination may be mediat ed by stimuli with high ecological salience. (C) 1997 Elsevier Science Inc.