Neonates' heart rate,sucking rhythm,and sucking amplitude as a function of the sweet taste

In previous studies of human newborn sucking, the effects of increasing fluid sweetness and/or volume included a decrease in sucking rate within sucking bursts and, paradoxically, an increase in heart rate. To determine whether the heart rate increase can be attributed to increased sucking amplitude for sweeter fluids, sucking and heart rates of 20 full-term infants were studied. Half sucked for three consecutive 2-min periods, first receiving small drops of water for each suck, then no fluid, then 15% sucrose. The other half experienced the reverse order. The results for sucking and heart rate were consistent with previous studies; sucking rates within bursts were slowest for sucrose and fastest for no fluid. Heart rate was higher for sucrose than for the other fluid conditions, however, only in the water-first group. The heart rate increase was significant on statistical tests which controlled for sucking amplitude as well as for several other motor variables. Sucking amplitude itself varied with fluid sweetness in the water-first group only, in which it was highest for water. There were more total sucks, longer sucking bursts, and less time between successive bursts under the sucrose condition. Multivariate statistics helped establish a set of dependent variables—sucking rate within bursts, total number of sucks, and heart rate—which most parsimoniously describes the effects of fluid sweetness. A hedonic explanation of the response of newborns to sweetness is thus reiterated.