Authors: Linda S. Pagani, Caroline Fitzpatrick, and Tracie A. Barnett.
Every hourly increase in daily television watching at 29 months of age is associated with diminished vocabulary and math skills, classroom engagement (which is largely determined by attention skills), victimization by classmates, and physical prowess at kindergarten, according to Professor Linda Pagani of the University of Montreal and the CHU Sainte-Justine children’s hospital.
http://www.nature.com/pr/journal/v74/n3/full/pr2013105a.html