UNICEF states that the early childhood years from birth through age 8 are formative in terms of intelligence, personality and social behavior. The first two years are particularly crucial.
People develop best intellectually, emotionally and inter-personally when their formative years are free of repression, natural disasters, malnutrition, polluted water and armed conflict, according to UNICEF.
The formative years of a child differ, however, based on the specific type of development in question. According to PBS, when considering the development of attachments to caregivers, the first five years of life are the most important. PBS indicates that therapy helps some adults develop attachments even when they are deprived of connections during their first five years.