The more time and energy moms shower on newborns—in terms of having full-term pregnancies and breast-feeding their children—the more big-brained the kids are likely to be, according to a study published in the Proceedings of the National Academy of Sciences and reported by ScienceDaily.

For the study, researchers evaluated the reproductive routines of 128 mammalian species (including humans). Findings suggested that babies would have the best brain development if they were exclusively breast-fed for six months then fed breastmilk and solid foods until age 2 or older. (This is the World Health Organization’s recommended infant feeding regimen.)

What’s more, the study helped show that human babies required a longer dependency period (being breast-fed for up to three years and sheltered in mom’s womb for nine months) to allow for the growth of their larger brains. (This isn’t so for smaller-brained mammals.)

These findings will “help us understand what the implications are of evolutionary changes at different stages, before and after birth,” explained Robert Barton, MSc, PhD, an anthropology professor at Durham University in England and the study’s lead researcher.

What’s next? Researchers need to find out how changes during babies’ pre- and post-birth growth phases affect the structure of the brain, Barton said.

Click here to learn how breast feeding may also help school-aged kids.