In the study by Lee Salk, reported in Case Study 1.1, he found that infants who listened to the sound of a heartbeat in the first few days of life gained more weight than those who did not. In searching for potential explanations, Salk wrote the following. Discuss Salk’s conclusion and the evidence he provided for it. Do you think he effectively ruled out food intake as being important? In terms of actual weight gain the heartbeat group showed a median gain of 40 grams; the control group showed a median loss of 20 grams. There was no significant difference in food intake between the two groups. . . . There was crying 38 percent of the time in the heartbeat group of infants; in the control group one infant or more cried 60 percent of the time. . . . Since there was no difference in food intake between the two groups, it is likely that the weight gain for the heartbeat group was due to a decrease in crying (Salk, May 1973, p. 29)