Mastering prosody is a different task for adults learning a second language and infants acquiring their first. While prosody crucially aids the process of L1 acquisition, for adult L2 learners it is often considerably challenging. Is it because of an age-related decline in the language-learning ability or because of unfavorable learning conditions? We investigated whether adults can auditorily sensitize to the prosody of a novel language, and whether such sensitization is affected by orthographic input. After 5 minutes of exposure to Māori, Czech listeners could reliably recognize this language in a post-test using low-pass filtered clips of Māori and Malay. Recognition accuracy was lower for participants exposed to the novel-language speech along with deep-orthography transcriptions or orthography with unfamiliar characters. Adults can thus attune to novel-language prosody, but orthography hampers this ability. Language-learning theories and applications may need to reconsider the consequences of providing orthographic input to beginning second-language learners.

As a western Slavic language of the Indo-European family, Czech is closest to Slovak and Polish. It is spoken as a native language by nearly 10 million people in the Czech Republic (Czech Statistical Office n.d.). About two million people living abroad, mostly in the USA, Canada, Austria, Germany, Slovakia, and the UK, claim Czech heritage (Ministry of Foreign Affairs of the Czech Republic 2009). However, it is not known how many of them are native speakers of Czech.