Perceiving and producing English phonemic vowel length contrasts is challenging for non‐native speakers. According to multi‐time resolution models, endogenous slow/fast rhythms contribute, respectively, in the right/left hemispheres, to long/short acoustic cue processing. This study introduced a perceptual training method implementing dichotic stimulation to improve /i:/‐/ɪ/ processing by promoting hemispheric complementarity. Twenty non‐dyslexic and 20 dyslexic French adults received 1 hr‐training over 3 days. Productions were evaluated with pre‐/post‐tests. Training enhanced vowel duration contrast in word production by /i:/ lengthening and /ɪ/ shortening in both groups. Adults with dyslexia compensated fewer /i:/ lengthening by /ɪ/ shortening than did non‐dyslexic adults. Transfer from perceptual training to production seems possible for foreign‐language learning even in dyslexic adults. The extent to which dichotic presentation contributed to training effectiveness cannot be evaluated here, but the triggering of lengthening and shortening mechanisms suggests that lateralized complementary skills have been enhanced by dichotic stimulation.