“There was a lot of focus on how relationships with mothers were very important, and there was very little thought about other social relationships,” says Michael Lamb, a psychologist at the University of Cambridge who has been studying fathers since the 1970s. “The most obvious of those was the father-child relationship – a relationship that was viewed as more important as children grow older, but was always viewed as secondary to the mother-child relationship.”

Or as Marian Bakermans-Kranenburg of Vrije Universiteit Amsterdam, who is doing a series of studies on new fathers and family relations, puts it: “Half of parents are fathers, yet 99% of the research on parenting focuses on mothers.”

Now, new research is showing that the social world of children is much richer, and more complex, than previously thought.

It is not just dads who have moved into the spotlight. Grandparents, same-sex parents, step-parents and single parents have also helped researchers understand what really makes a child thrive – and that it’s not just about one caregiver.

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“Part of the argument that I’ve been trying to make for the past 45 years is that actually, no, there are multiple important factors,” says Lamb. “We do want to recognise differences in their importance, but we also need to recognise that – to quote that cliché – it does take a village, and that there are a lot of important relationships that shape children’s development.”

A range of recent studies show how flexible parenting roles can be. Psychologist Ruth Feldman of Israel’s Bar-Ilan University has found that, just like mothers, fathers experience a hormonal boost when caring for their babies, which helps the bonding process. When dads are the main caregivers, their brains adapt to the task.

And emotional involvement matters. Babies with emotionally engaged dads show better mental development as toddlers and are less likely to have behavioural problems later on, compared to babies whose dads behave in a more detached way. Older children benefit, too. Those whose fathers, or father figures, are more emotionally supportive, tend to be more satisfied with life and have better relationships with teachers and other children.