Bowlby's attachment talks about the primary caregiver, it does not specify mother or father, even though it is mostly the mother. I want to know more about the specific roles of the father and mother in the process of attachment. I've read some studies than mention some differences.
Freeman & Brown(2001) examined attachment for adolescents, they used the Adolescent Separation Anxiety Test to evaluate this population, they found the mother is most often the primary source of attachment.
Main & Cassidy (1988) found that the infant attachment was less predictive of the attachment style at six years of age for the father than for the mother.
What are the studies that talk about the differences between mother and father in attachment?
Freeman, H., & Brown, B. B. (2001). Primary attachment to parents and peers during adolescence: Differences by attachment style. Journal of Youth and Adolescence; New York, 30(6), 653–674. http://dx.doi.org/10.1023/A:1012200511045
Main, M., & Cassidy, J. (1988). Categories of Response to Reunion With the Parent at Age 6: Predictable From Infant Attachment Classifications and Stable Over a 1-Month Period. Developmental Psychology, 24(3), 415–426. https://doi.org/10.1037/0012-16188.8.131.525