Normal Heartbeat Sound and the Behavior of Newborn Infants‐‐A Replication Study

&NA; A group of infants exposed to a simulated heartbeat sound at 45 decibels during the first 4 days of life did not respond differently in terms of weight gain, activity, or formula intake from a group of control infants not so exposed. A significant positive correlation between weight gain and food intake was noted. Some of the pertinent differences between this replication and the previous study by Salk are considered in an effort to clarify some of the questions of design and the differences in findings.