by Martine Danan (Translators' Journal - vol 40 -n°1)

"Audiovisual material enhanced with captions or interlingual subtitles is a particularly powerful pedagogical tool which can help improve the listening comprehension skills of  second-language learners. Captioning facilitates language learning by helping students visualize what they hear, especially if the input is not too far beyond their linguistic ability.
Subtitling can also increase language comprehension and leads to additional cognitive benefits, such as greater depth of processing