Before they were married, Bill and Tanya were determined to have an egalitarian relationship, sharing household tasks and childcare. But after the birth of their first child, Jason, Tanya found herself doing the majority of the childcare, and Bill found himself working longer hours at his job. This is an illustration of what theoretical principle or concept?

The parental imperative theory is a gender identity theory that holds the belief that while raising a child both father and mother hold a distinct role. The theory is based on the traditional gender role where male and female play different role in raising a child. This theory is criticized by many scholars for stereotyping gender roles.

As per the question, the different gender roles played by the Bill and Tanya while raising their child upholds the belief of parental imperative theory.