We chose commercially available books for this study so that these materials could be most easily
implemented in other classrooms.Because of this,the exact structure of the stories and the words that
we included were some what different a cross themes.To address this issue,we slightly modified the
texts of the books so that they included exactly one usage of each of the Target and Exposure words.
We additionally ensured that all four books were matched for overall length,total number of words,
number of words per page,and total number of pages.In addition,we integrated all of the words into
the books in parallel ways,so that they were all represented by pictures in the books and were all
equally important to the action.