http://www.slate.com/articles/life/family/2015/10/how_my_3_year_old_son_and_i_gave_up_our_blankies.html

Picking up my son at day care, I hesitated outside the sliding glass door. The older kids—the ones who compete like world-class bird-watchers to spot arriving parents—hadn’t seen me yet. I had the chance to observe my 3-year-old playing quietly with a bulldozer in the corner, all by himself. On the other side of the playroom, I couldn’t help noticing teeth marks on the neck of one of the younger toddlers.