This article presents an experimental study to investigate whether subtitle reading has a positive impact on academic performance. In the absence of reliable indexes of reading behavior in dynamic texts, the article first formulates and validates an index to measure the reading of text, such as subtitles on film. Eye-tracking measures (fixations and saccades) are expressed as functions of the number of standard words and word length and provide a reliable index of reading behavior of subtitles over extended audiovisual texts. By providing a robust index of reading over dynamic texts, this article lays the foundation for future studies combining behavioral measures and performance measures in fields such as media psychology, educational psychology, multimedia design, and audiovisual translation. The article then utilizes this index to correlate the degree to which subtitles are read and the performance of students who were exposed to the subtitles in a comprehension test. It is found that a significant positive correlation is obtained between comprehension and subtitle reading for the sample, providing some evidence in favor of using subtitles in reading instruction and language learning. The study, which was conducted in the context of English subtitles on academic lectures delivered in English, further seems to indicate that the number of words and the number of lines do not play as big a role in the processing of subtitles as previously thought but that attention distribution across different redundant sources of information results in the partial processing of subtitles.