At the center of Sterling's creation are several strategies for getting girls to build: engage them with a story, challenge them to build with a problem-solving purpose, use materials that are warm or soft to the touch (no metal) and have shapes with curved edges, and presented in colors that American girls in the year 2012 tend to be attracted to. The toy set includes the story of its heroine, "GoldieBlox and the Spinning Machine" (available as a book or iOS app), five character figurines (Goldie's "friends"), and building kit that includes plastic elements and a ribbon.

The premise is that as Goldie's story unfolds, she builds different devices that help her accomplish certain tasks. Every time the "build" icon appears, girls following along have to build along with her in order for the story to continue. For example, in the book's first story, Goldie needs to build a spinning machine for her dog. "There's just this moment of excitement for a girl when they wrap this ribbon around this wheel and they pull it and it spins," Sterling says. "It's such a basic engineering principle of a wheel spinning on an axle, but it is this magical moment for every girl I have tested."

Since most girls are used to playing with static toys, Sterling points out, the simple act of creating motion can prove to be exciting for them.

As the book progresses, the building projects get more complex, and the girls have to create contraptions that can spin more and more of the story's characters. Sterling recalled, "I kept hearing the same thing over and over again: Girls saying 'I want to spin all the animals! I want to spin all the animals!' They get really into it. Rather than just tossing the construction element aside and just play-acting with the characters (which is what I thought might happen), they really wanted to build."

Part of Sterling's hope is that by getting girls to build for Goldie, they'll come to see building and design as something that can have their own social value. "Girls really want to help people and they care about nurturing," she says. "When you think about how back in the day, most doctors were male. As women began to gain more power, guess who starts to become doctors? Women. Because they love nurturing and caring about people -- it was an obvious step. I think the same thing will happen with engineering, once we learn what engineering really is and we get beyond the stereotype of a nerdy man sitting alone in a cubicle at a computer. Engineers are solving some of the world's biggest problems and helping people."

Sterling's basic conceit -- that by playing to girls' inclination to help and imbuing their designs with practical purpose she can get them designing and building -- is echoed in the work of Christine Cunningham, a vice president of the Museum of Science in Boston and director of the Engineering is Elementary program. Like Sterling, Cunningham has found that if you embed an engineering dilemma in a story, girls will have more interest in figuring out the challenge. For example, she says, kids' kits for electrical engineering, which is one of the most heavily male of the different kinds of engineering, tend to ask kids to build circuits to make a light turn on or a fan blow air. When Cunningham set about to redesign an electrical-engineering activity with girls in mind, she and her team embedded it in a story about a girl living on a ranch who needs to keep a trough filled with water for the baby lambs. The character decides to build herself an alarm as a reminder. That gives girls a purpose, and they'll "engage in the same tasks and have the same sort of outcomes, because they're linking it back to the safety of the baby lambs," Cunningham told me.