Infancy is a time of intense development. Babies start out with little more than instinctual reflexes and an innate ability to learn. Over the course of two years, they progress to the point where they have recognizable personalities; are able to move themselves from place to place and manipulate things; and understand how certain important aspects of the world operate (such as object permanence; the understanding that objects continue to exist even when you are not looking at them). They understand the rudiments of how to make their wishes known, have formed attachments and relationships, and have learned basic ways of managing their emotions and impulses. While these achievements are tremendous and set the stage for later learning, they are also commonplace. So long as children are born without significant illness, and so long as they are properly nurtured and cared for, their development towards these achievements will likely progress uneventfully.
The key phrase is, of course, "properly nurtured." As Bronfenbrenner stressed, child development is influenced by the environment at every level. Children progress toward milestones through interaction with their physical environments, with loving parents, and with the larger world. Problematic or lack of nurturing has a negative impact on their ability to progress smoothly. Children who are not exposed to language and communication stimulation, either because of hearing problems or caregivers' neglect to speak with and around them, can have difficulty learning more complex language skills in later years. Similarly, children who are deprived of consistent nurturing care can grow to learn to mistrust others and have problems bonding with caregivers or other people in later years. Good parenting skills can help smooth out some of the inevitable bumps and bruises that might threaten to derail more sensitive or temperamental children. Though all parents will make mistakes in the 22 years it takes to raise a child; love, attention, and care provide strong bedrock for healthy child development.
Development doesn't stop here, of course. When it is ready, the next document in this series will discuss how children progresses into the next stage of development, the preoperational stage, which lasts from ages 2 through 7.