Does that mean the first 3 years of our children's lives are the most important in terms of brain development?
Yes, 3 years and 9 months! There is a lot of research around for in utero brain development. One thing that we know is that the parts of the brain that organise emotional memory are fully mature by the time we are born. Our bodies can recall emotional memory from before birth. You can be 50 years old and be triggered into emotions that you were feeling when you were 8 months in the womb. Consciousness is well developed by the third trimester; not so much a 'self-consciousness' but the awareness and ability to feel every human emotion. Things that the mother goes through effect the baby most and have the biggest impact in the third trimester.
The empathy centers of the child's brain grow according to the empathy that the child receives. All of the loving experiences that come naturally to parents; the eye contact, the playfulness, touch and tenderness: all of those empathic, joyous and pleasurable experiences, generate new brain growth in a child's empathy and impulse control centers. One of the mechanisms for this is the experience of intimacy; this produces a lot of the love hormone oxytocin. Oxytocin generates the growth of new neuro pathways in the brain. Loving contact with little children and babies, is literally adding mass to the brain. Not any old place where the IQ of a child grows, but the empathy centers which create emotional intelligence.
http://our-emotional-health.com/about.html
http://hearttoheartparenting.org/
IMAGE CREDIT: Kelly Jordan