Marshmallow masquerade

Puzzled by what makes boys tick, 17-year-old identical twins Chris and Susan Pratt hatch a clever plan: Chris will go undercover as a boy, pretending to be ?Charlie? for a week.  Chris isn?t only surprised by what she learns about the boys she knows?and thought she knew?she also learns unexpected lessons about the roles both boys and girls are programmed to play.  Young Adult Fiction by Cynthia Blair; originally published by Fawcett Juniper