Context constraints, prior vocabulary knowledge and on-line inferences in reading

linguistic stimuli in reading. Available prior knowledge about the language and about the world facilitates not only comprehension of the explicit information in the text, but also the generation of inferences about implicit information (e.g., McNamara & Kintsch, 1996). Vocabulary or word knowledge is a major component of prior knowledge that has been found to be related to inferences in reading. Thus, high vocabulary readers are more likely than low vocabulary readers to draw both connective (Singer, Andrusiak, Reisdorf & Black, 1992) and elaborative (Dixon, LeFevre & Twilley, 1988) inferences in adult readers. The aim of the present study was to investigate to what extent the beneficial influence of prior vocabulary knowledge on elaborative inferences during reading depends on the degree of contextual constraints (i.e., how much a context sentence suggests a tobe-inferred concept). This approach will be useful, first, to determine whether high vocabulary knowledge allows the drawing of inferences even when context constraints are reduced. Thus, if the facilitating effect of high vocabulary knowledge is strong, this effect should also occur with low context constraints. Second, this approach will show whether low vocabulary readers benefit from enhanced context constraints; that is, whether enhanced context constraints play a compensatory role for these readers, enabling them to perform similarly to high vocabulary readers. More specifically, this study is concerned with a major type of elaborative inference, such as predictive inference, also called forward inference, which has received a great deal of attention in reading research (e.g., Calvo & Castillo, 1996; Fincher-Kiefer, 1995; Keefe & McDaniel, 1993; Klin, Guzmán & Levine, 1999; McKoon & Ratcliff, 1986). Predictive inferences are anticipatory representations of the likely outcomes of described events. Thus, we draw a predictive inference if, when we read that «someone fell from a 14th story window», we think or imagine that «s/he died». Context constraints in predictive inferencing refer to how much a sentence context suggests an implicit event outcome (thus, for example, the sentence «falling from a 14th story window» would constrain the inference «death» more than the sentence «falling from a 3rd floor window»). Context constraints have been proposed to be a critical factor in determining whether or not predictive inferences will be made on-line during reading (Graesser, Singer & Trabasso, 1994; Klin et al., 1999). Furthermore, it has been found that the time course of these inferences varies as a function of context constraints, with inferences being made earlier as constraints increase (Calvo, 2000). Accordingly, our approach regarding the role of context constraints on the contribution of prior vocabulary knowledge to elaborative inferences is relevant to an important theoretical issue. Context constraints, prior vocabulary knowledge and on-line inferences in reading