                          tence 1: Because of rapid brain growth and  radual decline in brain plasticity, the first 5 to 8  ears of life are regarded as a sensitive phase of  fevelopment in which appropriate stimulation is  jecessary for children to reach their full genetic  tential.    tence 2: The first 5 to 8 years of life are  egarded as the least sensitive phase of  fevelopment.