Schaffer and Emerson found, when looking into the role of fathers as secondary attachment figures, that within a few weeks or months of the primary attachment, the infants formed secondary attachment to other family members, e.g. the father. In 75% of the infants studied, an attachment was formed with the father by the age of 18 months. This was determined by the infants protested when their father walked away (separation distress). So fathers are more likely to be secondary attachment figures that infants receive added support from, and provide an emotional safety net.