BOWLBY: women better caregivers (sensitive, biological)
+ SCHAFFER + EMERSON (mothers likely, 75% father at 18 months)
PLAYMATE: physical activity, problem-solving
+ GROSSMAN (less influential except play)
+ LAMB (quality time > amount)
+ sensitivity > involvement
+ ANG (teacher, predictive validity)
-. BIBLARZ + STACEY (temporal validity)