Publication Date


Document Type


First Advisor

Britt, Mary A.

Degree Name

M.A. (Master of Arts)


Department of Psychology


Cognitive psychology


Previous research has shown that students experience difficulty understanding scientific texts that explain physical systems (e.g., how coral bleaching occurs; how speakers work). Explanatory texts about physical systems depict causally connected components and events that change across time and space. Readers incrementally build a mental representation of the system often called a mental model. The primary goal of the present experiment was to explore the possibility that one reason why explanatory texts are difficult to comprehend is that students adopt reading goals that do not facilitate the construction of a coherent mental model of the explanation. In the present experiment, participants were given one of three task instructions before they read and reread explanatory texts about scientific processes. It was assumed the task instructions would affect participants' reading goals and the emphasis that they place on encoding causal and spatial attributes of the described mechanism. The baseline instruction was to "read for understanding". A task instruction which was thought to emphasize causality was to "read to explain" the physical system to a friend. The third task instruction, which was thought to emphasize spatiality, was to "read in order to draw" the system. Sentence reading times were collected for the initial and second reading of each passage. The sentence reading times were later predicted using linear mixed effects modeling from control variables (e.g., sentence length, passage order), and theoretically interesting variables (i.e., general, spatial, and causal processes) taken from two models of mental model updating. Sentence reading times have been used extensively by reading researchers as an indirect measure of the mental processes that contribute to understanding written discourse. It was assumed that if a variable predicted reading times (e.g., the number of causal links expressed in a sentence) above and beyond the control variables, it would indicate that variable was being used in the creation of the mental model of the system (e.g., constructing causal connections). Competing hypotheses were postulated regarding how the different task instructions may moderate the relation between the theoretically relevant variables and sentence reading times and how these relations may change across readings. The results revealed that the general and spatial variables predicted sentence reading times for both readings and in each of the task conditions. There was little difference between the first and second readings on the pattern of statistically significant predictors except for one finding: in the first, but not second reading, sentences which contained more explicit causal relations were read slower than sentences which contained fewer causal relations. However, this relationship only occurred for participants who read to draw the system than participants who read for understanding. This finding suggests that reading "to draw" the explanation encourages the reader to make causal connections, at least for an initial reading. Interestingly, the goal to explain appeared not to emphasize causality in their understanding of the system. Nevertheless, the findings provide evidence that readers differentially allocate resources to mental model construction as a function of task instructions. More importantly, the findings suggest that one reason why readers have difficulty understanding scientific explanations is that they are not emphasizing causality in their mental models. More research is needed to address this possibility. Although measures of individual differences (e.g., spatial ability, reading ability) and their resulting mental models (i.e., recall) were collected, they were not analyzed for the purpose of this thesis. The findings were discussed in relation to models of comprehension and prior research.


Committee member: Magliano, Joseph P.||Advisors: Britt, Mary A.; Millis, Keith K.||Includes illustrations.||Includes bibliographical references.


87 pages




Northern Illinois University

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