1. In “The Early Catastrophe”, Hart & Risley provided a figure that demonstrates the vocabulary size trajectory of the children in the study, stratified by age group (page 4). It appears that the trajectory of vocabulary size between children of middle/lower SES versus those on welfare remains very similar until about 23 months of age. This made me wonder why it is that the vocabulary size trajectory seems to dramatically increase around this age among children of lower/middle SES families, in comparison to children from families on welfare? Furthermore, I also wondered why the authors chose to combine the middle and lower SES families into one category when reporting the results. Even if there were no differences between these two categories,
