"She's never seen a television show in her life," says Cassidy's father, Allen Kanner, who works as a parent and a child psychologist. "It's not a problem: When she's left by herself, she takes out her blocks and starts to create a little fantasy world for herself."
"She has a very active imagination, which I think has a lot to do with not watching television," he says.
According to Dr. Dimitri Christakis, the George Adkins professor of pediatrics at the University of Washington and Seattle Children's Research Institute, Cassidy is doing a whole lot more than entertaining herself when she plays with blocks.
"Manipulating play helps language development," says Christakis. "When a child is playing with a truck, they are in fact, saying, 'Truck' internally."
In a term psychologists call "scaffolding," Cassidy might be silently talking to her toys in ways that help her understand language, Christakis says. Anderson says similarly focused, manipulating play helps toddlers develop skills to plan ahead intelligently, for example, to use a flat surface to help build or to put bigger blocks on the bottom.
"Those sorts of connections are happening beneath the surface, even though parents can't see them," says Christakis, who also wrote a book on the subject of household television called "The Elephant in the Living Room: Make Television Work for Your Kids."
At the moment, studies seem to show television at a young age interferes with learning.
"There have been a lot of studies that explored this, and early television is associated with delayed language, delayed cognitive developments, shorter attention span," Christakis says. "What we haven't found yet is the mechanism."
Kanner says he chose a no-television household before Cassidy was born not as an experiment but as life for himself and his children. But for parents who don't want to abandon the television, experts say there's some control measures to take beyond counting hours.
"Try not to commingle play and television," says Schifrin. "Play is skill building -- physical, mental, emotional, behavioral skills. There is very little skill in watching television; we're all very good at that."
And finally, "Don't put a television in the bedroom," Schifrin says. "We're trying to create an amnesty program for bedroom televisions -- we'd like to go into every house and rescue these televisions from the kid's bedrooms."