My experience as a language learner (French) supports the study. When I use English (native language) subtitles, my listening doesn't improve at all. However, my improvement with or without French subtitles depends on my level of comprehension. If I can understand most of the show without subtitles (~60% or more) I improve faster without subtitles. If I understand half or less, I improve with the subtitles. I guess this is evidence for Stephen Krashen's theory of comprehensible input.