Amid Father's Day celebrations this week, many young dads will be harboring a little secret guilt: They feel they should be more like moms -- traditional ones, that is, who spend a lot of time at home. My email bears evidence: One father, a salesman, writes that he feels guilty for not taking paternity leave but he fears damaging his career. Another says he's "scared about long-term effects" of his heavy business travel on his two small children.

If a dad can't be Mr. Mom, what can he be? A growing body of research offers...