As many parents know well, some young children can easily moderate their emotions, while others struggle to do it. Some toddlers can cry for long periods of time when they don't get what they want, a behavior that can start early. The big questions are: Does it happen just by luck of the draw? And, what does science know about it? To begin with, it may be useful to clarify what "difficult" means, as well as difficult for whom, and why.

According to Meghan Leahy, a mother of three daughters and the author of the book "Parenting Outside the Lines," some children are born more intense than others. She uses the word "intense" because she finds the word "difficult" pejorative and not descriptive enough. First, we need to understand the idea of temperament. "Temperament is a rating scale that assesses a child’s early-appearing variation in emotional responses and reaction to the environment. Is your baby quick to be active? Is your child regular in routine? Quick to warm up to new people and places?" asks Leahy.

Even more than intelligence and talent, temperament has long been considered as a purely genetic and fixed element of personality; basically, a child is born that way and will remain so. However, research about twins, siblings and adoption have shown that temperament is much more adaptable and flexible than believed in the past. Actually, babies are capable of change all along their development and can be decisively affected by parenting styles, for better or for worse.

In summary, science shows that our environment, thanks to the incredible plasticity of our brain, can have huge consequences on the evolution of our children's temperament.

Picture: Child with Headache (Wikimedia Commons, w/Effects)