"We have this theory that if we get content on multiple platforms and devices, it gives kids and families a chance to reinforce and experience the curriculum multiple times, " says Terry Fitzpatrick, executive vice president of content and distribution for Sesame Workshop, who emphasizes videos are best co-viewed with child and parent.

NPR: 'Sesame Street' Nears 1 Billion Views On YouTube

Germany's example is especially instructive: Although the state's family policies are now among the most generous in Europe -- a parent who stays home with a child receives 67% of his or her current net income for up to 12 months -- they have failed to boost the birthrate or reverse the figures for childless women.

CNN: Why are rich nations' birthrates in free fall?

Parents often torpedo their discipline efforts by giving vague, conditional commands and not giving kids enough time to comply with them, says Dr. Verduin, who practices parent-child interaction therapy.

WSJ: Smarter Ways to Discipline Children

Examples include a neighbour who regularly plays with their children or somebody new entering the lives of a child - such as a parent's new partner.

BBC: Sex offence disclosure scheme used by 156 parents

Oxytocin in particular is crucial in bonding partner to partner (levels correlate with the success of a relationship), as well as parent to child, even pet-owner to pet.

WSJ: Looking Beyond Oxytocin, the Love Drug | Marvels