Nancy Jensen, who took part with her now 6-year-old daughter, said the study was a wake-up call.
"I didn't realize how much Elizabeth was watching and how much she was watching on her own," she said.
Jensen said her daughter's behavior improved after making changes, and she continues to control what Elizabeth and her 2-year-old brother, Joe, watch. She also decided to replace most of Elizabeth's TV time with games, art and outdoor fun.
During a recent visit to their Seattle home, the children seemed more interested in playing with blocks and running around outside than watching TV.
Another researcher who was not involved in this study but also focuses his work on kids and television commended Christakis for taking a look at the influence of positive TV programs, instead of focusing on the impact of violent TV.
"I think it's fabulous that people are looking on the positive side. Because no one's going to stop watching TV, we have to have viable alternatives for kids," said Dr. Michael Rich, director of the Center on Media and Child Health at Children's Hospital Boston.
Contact AP Writer Donna Blankinship through Twitter (at)dgblankinship