Anyone who takes on the role of the main male caregiver, not necessarily biologically related.
Klaus Grossmann
Longitudinal study where attachment was studied from baby until teen, focussing on parent's behaviour and quality of baby's later attachments
Found that the attachment to mother's is related to later attachments, and father's are responsible for play and stimulation.
Tiffany Field
Filmed 4 month old babies interacting with:
primary caregiver mothers
secondary caregiver fathers
primary caregiver fathers
Found that primary caregiver fathers spent more time interacting with the baby than secondary caregiver fathers, showing that fathers have the potential to be more emotion focussed, but perhaps only when the primary caregiver.
Role of father: Strength
Offers advice to parents in the real-world, regarding who should stay home. Also reassures same-sex couples of their child's development
Role of father: Weakness
Grossmann's research has the potential for unintended observer bias, due to the stereotypical images of fathers in the media. They could have been observing what they expected rather than objective reality.
Shaffer and Emerson
3% of cases the father was the sole attachment figure
27% father was the first joint attachment with the mother
Mothers are usually the first attachment but strong attachments to the fathers do follow