Mann's previous research has shown that dolphin
mothers pass the sponging
method to their daughters and some of their sons, rare evidence of a cultural tradition in an animal
other than humans.
Using different
methods, and examining families in the United States and abroad, the results are encouraging: children who spend at least 35 percent time with each parent, rather
than live with one and visit the
other, have better relationships with their fathers and
mothers and do better academically, socially, and psychologically.