Not just moms, a new dad's heart too pours for his or her toddler the moment he looks at him or her playing.
Now, researchers have documented definite structural changes in the brains of new fathers as they spend more time with their kids.
They suggested that some parts of the brain increased in size when fathers looked at their children.
"Lab research on animals implicates many of these neural regions as important for attachment and nurturing behaviours," said lead researcher Pilyoung Kim from Denver University, the US.
During the study, Kim and his team scanned brains of 16 new fathers and found increased grey matter in many regions.
This included areas involved in reward processing, hormonal control, emotional processing, memory and decision making.
Some regions of the brain also shrank in early fatherhood. This part of the brain tends to become more active as we switch off from the outside world.
According to researchers, the shrinking of the brain regions could reflect a shift of resources - in line with fathers' new vigilance for their kids.
Researchers think that this shrinkage could reflect a reduction of fathers' anxiety in the first few months of their infants' lives.
The study was published in the journal Social Neuroscience.
