In the United States, as in the United Kingdom, we've just celebrated the centennial of Father's Day. (It was first introduced a century ago, but didn't become a legal holiday until 1966.) But just what are we celebrating? For decades, pundits have been heralding the birth of the new father. Has he finally discarded his pupae stage and emerged a full-fledged multi-faceted, multi-tasking parental butterfly?

Well, yes and no. The evidence from two decades of social science research paints a complicated picture. On the one hand, most American men now find themselves in a dual-career couple, in which both adults work outside the home. Across Europe and the US young married men assume their wives will work outside the home, and assume – and desire – a more active and engaged fatherhood than they often experienced with their own fathers.

The average American father spends three hours a day on the weekend with his family – up significantly from estimates in earlier decades. Men are more likely to hug their children and tell them that they love them than in previous decades. A poll in Newsweek magazine found that 55% of fathers say that being a parent is more important to them than it was to their fathers, and 70% say they spend more time with their children than their fathers spent with them.

On the other hand, a dual-career couple doesn't necessarily mean a "dual-carer" couple. Men's participation in housework and childcare continues to be best expressed by two two-word phrases – we "help out" and "pitch in". We don't quite "share."

In both Europe and the United States, men's increased participation in childcare also carries some dangers. In many middle-class families, dad is becoming the "fun parent". He takes the kids to the park and plays soccer with the kids; she stays home. "What a great time we had with Dad!" the kids announce as they burst through the kitchen door to a lunch mum prepared while also folding the laundry and vacuuming the living room.

American men's participation in family life lags behind the rates of participation in other industrial countries. In Australia, Canada, and the Netherlands, men's rates are about double the rates in the US, while in Britain the rates are about 40% higher. It's amazing what state policies that enable work-family balance, such as paid parental leave, can do for involved childcare. (In fact, the US is one of only five countries that offer no paid parental leave to either parent — the others, according to research by the Project on Global Working Families at McGill University in Canada are Swaziland, Liberia, Lesotho and Papua New Guinea.

Since we can't always rely on the opportunity provided by state policy, we have to rely on increasing men's motivations. Simply put, if American men are going to become the fathers they say they want to be, we have to show them that it is in their interests to do so. Fortunately, the evidence points decidedly in that direction.

Research by sociologists Scott Coltrane and Michele Adams looked at national survey data and found that when men increase their share of housework and childcare, their children are happier, healthier and do better in school. They are less likely to be diagnosed with ADHD, less likely to be put on prescription medication, and less likely to see a child psychologist for behavioural problems. They have lower rates of absenteeism and higher school achievement scores.

What's more, when school-aged children do housework with their fathers, they get along better with their peers and have more friends. And they show more positive behaviours than if they did the same work with their mothers. "Because fewer men do housework than women," said Adams, "when they share the work, it has more impact on children." Fathers model "co-operative family partnerships".

When men share housework and childcare, it turns out, their partners are happier. (This is intuitively obvious.) Wives of egalitarian husbands, regardless of class, report the highest levels of marital satisfaction and lowest rates of depression, and are less likely to see therapists or take prescription medication. They are also more likely to stay fit, since they probably have more time on their hands.

And the benefits for men are even greater. Men who share housework and childcare are healthier – physically and psychologically. They smoke less, drink less, and take recreational drugs less often. They are more likely to stay in shape and more likely to go to doctors for routine screenings, but less likely to use emergency rooms or miss work due to illness.

They're also psychologically healthier: they see therapists, are diagnosed with depression, and take prescription medication less often. They report higher levels of marital satisfaction. They also live longer, a finding that caused the Economist to quip "Change a nappy, by God, and put years on your life".

Oh, and they have more sex. Research by psychologist John Gottman at the University of Washington also found higher rates of marital sex among couples where men did more housework and childcare. This last finding was trumpeted by Men's Health magazine with the headline "Housework Makes Her Horny" (although I suspect that is less true when she does it). It is probably worthwhile pointing out that these are what social scientists call "aggregate" statistics, over the long-term. There is no one-to-one correspondence and so I would advise male readers of this essay not to harbour any expectations if they rush home upon reading this essay and begin to load the washing machine.

But load it they should. The evidence is clear that the more men share housework and childcare, the happier and healthier are their loved ones – as well as the men themselves. Fatherhood is not simply a state of being; it's a set of practices, things people do. And when men share those tasks that are normally called "parenting" everyone benefits.