ABSTRACT
In his classic 1944 article titled “Fundamental Factors in Reading Comprehension,” Frederick B. Davis wrote, “It is clear that word knowledge plays a very important part in reading comprehension” (p. 191). Davis’s statement has been used often, perhaps glibly, as a truism about the connection between vocabulary and reading comprehension. Indeed, there are various relationships between word knowledge and text understanding (Anderson & Freebody, 1981; Baumann, 2005; Nagy & Scott, 2000). Although it may be “clear” that vocabulary “plays a very important part in reading comprehension,” the simplicity of the assertion belies its knottiness, as was acknowledged by the National Reading Panel (NRP) (2000): “Precisely separating the two processes is diffi cult, if not impossible” (pp. 4-15). Further, it may be conventional wisdom that vocabulary knowledge affects reading comprehension directly, but, as Baumann, Kame’enui, and Ash (2003) noted, “The evidence of a causal link between vocabulary and comprehension is historically long but empirically soft” (p. 758).
