Two studies of children?s learning of new words during shared book reading: an inquiry into the effectiveness of low or high demand and extratextual questions on children?s learning of new words from stories, and an examination of the association between children?s acquisition of targeted words and the use of questions of high, low, and transitioning from low-to-high demand, based on samples of 59 and 50 children, respectively, from 4 suburban, affluent preschools