I believe that a potential third variable could be the temperament of the child. If a baby is generally in a happy mood, eats well, and sleeps well, then the parent is likely to want to spend more time with that child. Their relationship will grow, and they might have a stronger attachment than parents with infants with more difficult temperaments. The temperament of an adult can also have an effect on their well being. If they have an easy temperament, then they are likely to develop trusting and strong relationships, they are more likely to have more friends, and generally be happier. Thus, the temperament of a person could have an effect on both the attachment and the later well being of the individual.
