Social influences on formula intake via suckling in 7 to 14-week-old-infants.

To investigate social influences on human suckling behavior, 25 healthy, full term, 7 to 14-week-old infants were each bottle-fed their own formula twice by their mother and once in each of four experimental conditions: (a) held, provided social interaction; (b) held, without interaction; (c) not held, provided interaction; (d) not held, without interaction. Volume intake (VI), Total Sucks, infant gaze direction, and time elapsed since the last feeding were determined. There were three major findings: (1) social interaction increased VI; (2) VI was linearly related to the time since the last feeding in held infants; (3) Total Sucks and VI were both highly correlated with privation length when infants did not look at the feeder and when fed by the mother. Thus, social influences exert strong immediate impacts on suckling. Accordingly, suckling functions to obtain both nutrition from and social information about the feeder.