Final answer:
Holly is likely to invite same sex playmates to her birthday party, as research shows that children often choose peers who share similar gender-specific play interests.
Step-by-step explanation:
Based on the most consistent research findings, Holly is likely to invite same sex playmates to her eighth birthday party. Research has demonstrated that children tend to choose playmates and engage in play that conforms to gender roles and these preferences are often reinforced by the types of toys and activities parents provide and encourage. With the given knowledge that Holly plays with these playmates during recess and presumably has positive interactions with them, it's assumed that these are same-gender peers who share similar play interests. While alternative environments like Egalia preschool in Sweden aim to eliminate gender norms, more traditional settings often still result in children gravitating towards same-gender peers for friendship and play.