The current study investigated first language (L1) effects on listener judgment of comprehensibility and accentedness in second language (L2) speech. The participants were 60 university-level adult speakers of English from four L1 backgrounds (Chinese, Romance, Hindi, Farsi), with 15 speakers per group, performing a picture narrative task. Ten native English listeners used continuous sliding scales to evaluate the speakers’ audio recordings for comprehensibility, accentedness, as well as 10 linguistic variables drawn from the domains of pronunciation, fluency, lexis, grammar, and discourse. While comprehensibility was associated with several linguistic variables (segmentals, prosody, fluency, lexis, grammar), accentedness was primarily linked to pronunciation (segmentals, word stress, intonation). The relative strength of these associations also varied as a function of the speakers’ L1, especially for comprehensibility, with Chinese speakers influenced chiefly by pronunciation variables (specifically segmental errors), Hindi speakers by lexicogrammar variables, Romance speakers by variables spanning both pronunciation and lexicogrammar domains, and Farsi speakers showing no strong association with any linguistic variable. These results overall suggest that speakers’ L1 plays an important role in listener judgments of L2 comprehensibility and that instructors aiming to promote L2 speakers’ communicative success may need to expand their teaching targets beyond segmentals to include prosody-, fluency-, and lexicogrammar-based targets
