1.   However, no systematic observations have been made of maternal behavior and anxiety or of later infant development in these cases.

2.   By instinct, meaning that their maternal behavior is in some way programmed into their genes.

3.   His theory would not predict an effect of imprinted genes on maternal behavior such as removing the placenta, he said.

4.   So this theory would allow me, in an equal-opportunity twist, to blame my father for failing to endow me with good maternal behavior.

5.   Studies have linked oxytocin, which is also produced during childbirth and nursing, both with maternal behavior and with social affiliation.

6.   Still, it is a big leap to predict human maternal behavior from a pride of rats.