Elliemay, great post! You stated very clearly what I am learning in neuropsych this semester. It's called associative learning and it actually starts in the womb. The primitive brain forms neurons and synapses, and the environment outside the womb impacts the fetus inside. Loud music, fighting between mom and partner, physical violence - all are "learned" responses by the fetus and impact later responses by the baby, making him/her more fearful, fitful, etc. Conversely, a warm, nurturing environment prebirth (soothing music, less stress hormones like cortisol released due to loving relationship between mom and partner) give rise to a baby that is easier soothed and cries less. And, easier baby sometimes means easier less stressful relationship with mom which baby absorbs. And that cycle goes on and on into toddler-hood, childhood, etc. as the person grows and forms her own memories, behaviors, and individual characteristics and way of coping with life. And we carry this with us for a lifetime, either successfully or in some cases, changing as the need arises.

Whew! Hope that all makes sense