The brains in this image both belong to three-year-old children, yet the difference in size is dramatic.
What's even more dramatic is that the variations in volume and appearance are said to be down to how each child was treated by its mother or main caregiver.
UCLA's Professor Allan Schore, who has contributed to much of the ongoing research into this phenomena, says the growth of brain cells is a "consequence of an infant's interaction with the main caregiver," The Sunday Telegraph reported.
That is to say the growth of the baby's brain "literally requires positive interaction between mother and infant. The development of cerebral circuits depends on it."
The article adds that the way a baby is treated in the first two years of its life determines whether or not the eventual adult has a fully functioning brain.
It points out damage caused by neglect and other abuse can lead to lower intelligence, impaired ability to empathise, and a stronger susceptiblity to drug addiction and violent crime.
The work echoes the findings of child psychiatrists and neuroscientists at Washington University School of Medicine in St Louis.
The hippocampus is a key structure important to learning, memory and response to stress.
Published online in the Proceedings of the National Academy of Sciences Early Edition, lead author Joan L Luby said: "We found a very strong relationship between maternal nurturing and the size of the hippocampus in the healthy children."
She added: "Parents should be taught how to nurture and support their children. Those are very important elements in health development."
Brain size is also important in relation to a number of mental ailments including Alzheimer's, disease, depression and schizophrenia. Decreased brain volume is thought to contribute to these disorders, according to a report in the journal Nature Genetics.
Amazing Brain Facts