An article in a women's magazine says that women who choose to nurse their babies feel warmer and more receptive toward the infants than mothers who bottle-feed. The author concludes that nursing has desirable effects on the mother's attitude toward the child. Explain why asserting a cause-and-effect relationship based on this information is suspect, and give another plausible explanation for the association between the decision to bottle-feed or nurse and mothers’ attitudes toward their children.