We included threetypes of words:Target,Exposure,and Control(see Table 1 for full set of words).
Target words were taught through explicitde finitions, mode lusage in sentences,and illustrative
gestures. These words were used both in the book reading sessions and in the play sessions. Exposure
words were included in the book sand play sessions but were never explicitly taught.These words
were included to assess children’s abilities to learn words incidentally.Finally,Control words were
never present in either the book reading or play sessions but were included in the pre and post tests
to invest igate general vocabulary growth over the course of the two-week in tervention.
Each book contained 10 words that were the target of the intervention(Target words). Hence,each
child was taught 20 new words over the course of the intervention (2books with10 Target word seach).
Each book also contained 4or5 Exposure words for a total of 8(Realistic) or 9 (Fantastical) Exposure
words per theme.Eight Control words per the me were included in thepre-andpost-vocabularytests.
These words were chosen from listsin Biemiller (2009) to control for how well they are typically
known by four- year - olds .They were chosen to reflect avariety of formclasses(nouns,verbs,adjectives,
and prepositions),beabove preschoolers’ knowledge level,and (forthe Targetand Exposurewords)fit
naturally into the text of our chosen books. Apart from the seconstraints,words were chosenrandomly
from the list sand were randomly assigned toone of the three word types.Although all of the words
for all threetypes were matched for difficulty according to standardsde scribed in Biemiller (2009),