Children who are brought up by two parents grow up to be cleverer than those raised by just one person, new research suggests.
Being with both parents in the earliest years of life leads to a child developing more brain cells, the scientists believe.
However, the benefits vary between the sexes.
Being brought up by both parents causes boys to have better memory and learning functions.
By contrast, it causes girls to develop improved motor co-ordination and sociability.
It is believed that babies with two parents tend to get more attention and more stability, and that they are less likely to suffer emotional distress in the first years of life.
This leads to greater brain cell production – for boys it is grey matter brain cells that develop and for girls it is white matter brain cells.
The researchers from the Hotchkiss Brain Institute (HBI) of Calgary University, in Canada, studied mice and experimented by creating one parent and two parent family groups.
They then measured the offspring’s brain cell development from birth to adulthood.
Adult mice with the highest number of brain cells turned out to be those who had been brought up by two parents rather than one.
As babies they had received more attention and more nursing as both parents took turns to lick and tend to their youngsters, said HBI director, Dr Samuel Weiss.
As a result, the babies with two parents are less likely to suffer early life trauma which can have a massive impact on how their brains develop in later life, the research shows.
However, what did surprise the researchers is that female babies who grew up with both parents turned out to be good single mothers, as if good parenting was passed on.
Dr Weiss said: ‘Our new work adds to a growing body of knowledge, which indicates that early, supportive experiences have long lasting, positive impact on adult brain function.
‘Surprisingly, the advantages of dual parenting were also passed along when these two groups reproduced, even if their offspring were raised by one female.
‘The advantages of dual parenting were thus passed along to the next generation.’
Although the experiment was conducted on mice, many of the same principles of how early life events can influence growing up are relevant to humans too, the report added.
The researchers said: ‘In the mouse model, parenting and the environment directly impacted adult brain cell production.
‘It is possible that similar effects could be seen in other mammals, such as humans