According to the book, the percentage of infants that exhibit a secure attachment style is greater in households from the middle-class than in households from a lower socioeconomic status. Thus, I would argue that one variable which affects an infants future well-being is the socioeconomic status of their family. Although money doesnt necessarily buy happiness, I would predict that the percentage of infants that achieve a high level of well-being in later life increases with an increase in social class level
I agree. Families with different socioeconomic statuses tend to have different kinds or numbers of jobs, which may require the parents to spend different amounts of time away from home and their children, which could effect the child's type of attachment.