What Influences Gender Identity?

Do the gender stereotypes reflected (and exploited) in popular culture define and codify gender identity, or do they derive from fundamental, innate gender differences? To what extent do the messages about what it means to be male and female that we see in television, film, print, and web media influence our gender identities?

As you reflect on the gender stereotypes that pervade our culture, consider their implications: are they dangerous pigeonholes that limit understanding and personal growth (as many strident writers have noted), or are they less insidious charicatures, more deserving of playful mocking and armchair speculation (Dave Barry and Maureen Dowd) than passionate rebuke (Sut Jahlly and Jackson Katz in Tough Guise)? Additionally, what gender issues does screenwriter Tina Fey explore (and lampoon) in Mean Girls?