This study investigated the effects of mental imagery instruction using science expository texts on middle school students. Using a quasi-experimental pretest-posttest design, four intact classes (56 students) were randomly assigned to either an experimental or comparison group. Students in the experimental group received instruction on mental imagery strategies while comparison group students received no mental imagery instruction. After the 2-week intervention, students took Posttest 1. The comparison group students then received mental imagery instruction. Throughout the rest of the school year, all students were prompted at least two to three times a week to use mental imagery strategies. At the end of the school year, all participants took Posttest 2.

Results indicated that there was a statistically significant interaction of time and group for the selected response (SR) portion of expository science text comprehension measure. Both groups appeared to make gains between Posttest 1 and Posttest 2, once both had received mental imagery instruction. The comparison group, which by chance included stronger readers, outperformed the experimental group. There were no statistically significant differences on the brief constructed response (BCR) measure.

Analysis of the performance of low-, middle-, and high-comprehenders revealed statistically significant main effects for time and for type of comprehender on the SR portion of the comprehension task. While all students appeared to make gains between Posttest 1 and 2, the high- and middle-comprehenders consistently outperformed the low-comprehenders. For the BCR, there were no statistically significant effects of time or interaction; however, there was a statistically significant effect for type of comprehender. 

Pearson's product moment correlations revealed a statistically significant positive relation between vividness of mental imagery and motivation to read for middle-comprehenders and a statistically significant negative correlation between comprehension and vividness of mental imagery for high-comprehenders. Both experimental and comparison groups showed no statistically significant difference in motivation to read before and after mental imagery intervention. 

These results suggest that middle school students may benefit from mental imagery strategies when reading science expository texts. It is recommended that these strategies be used as a continuous effort in the classroom rather than a short term "quick-fix."