Final answer:
In the 1950s, experts did not widely advocate for fathers sharing primary caregiving responsibilities; parenting roles have since evolved. Caregiving was traditionally seen as a mother's role, with fathers being providers. Concepts like maternal feminism emerged, but equal parental roles in caregiving were not mainstream.
Step-by-step explanation:
In the 1950s, child development experts did not widely advocate for shared primary caregiving responsibilities among both mothers and fathers. Contrary to that notion, caregiving was predominantly seen as the mother's duty, with fathers often being the providers and less involved in the hands-on aspects of infant care. However, over time, there has been a significant shift in the understanding and practices of parenting roles. While John Bowlby developed the concept of attachment theory focusing on the bond infants form with their primary caregiver (traditionally the mother), later research by professionals like Mary Ainsworth expanded the understanding of caregiver and child attachment. Nonetheless, during the 1950s, the idea of maternal feminism was gaining traction, which argued for women's abilities to balance family responsibilities and roles in the wider world, but the shared parenting concept as it is understood today was not a mainstream concept at the time.