ERP evidence for implicit L2 word stress knowledge in listeners of a fixed-stress language.

Languages with contrastive stress, such as English or German, distinguish some words only via the stress status of their syllables, such as "CONtent" and "conTENT" (capitals indicate a stressed syllable). Listeners with a fixed-stress native language, such as Hungarian, have difficulties in explicitly discriminating variation of the stress position in a second language (L2). However, Event-Related Potentials (ERPs) indicate that Hungarian listeners implicitly notice variation from their native fixed-stress pattern. Here we used ERPs to investigate Hungarian listeners' implicit L2 processing. In a cross-modal word fragment priming experiment, we presented spoken stressed and unstressed German word onsets (primes) followed by printed versions of initially stressed and initially unstressed German words (targets). ERPs reflected stress priming exerted by both prime types. This indicates that Hungarian listeners implicitly linked German words with the stress status of the primes. Thus, the formerly described explicit stress discrimination difficulty associated with a fixed-stress native language does not generalize to implicit aspects of L2 word stress processing.

ERP correlates of word onset priming in infants and young children.

Using word onset priming with early learned words, we tracked access to phonological representations and predictive phonological processing at 6, 12, 18, and 24 months after birth. Event-Related Potentials (ERPs) were recorded while participants heard German word onsets (primes) followed by disyllabic spoken words (targets). Primes and target onsets were either congruent or incongruent (ma - Mama vs. so - Mama [Engl. 'mommy']). For an adult control group, ERP differences were found for the N100 complex, which has been related to abstract auditory analysis; and for the P350 deflection, which has been related to lexical access. A combined analysis of all infants and young children revealed an immature instance of an N100 effect, suggesting adult-like abstract speech sound processing. A central negativity effect, which had formerly been obtained when adults or older children were engaged in a lexical decision task, suggests that adult-like predictive phonological processing is available early in infancy. However, the absence of a P350-like effect in the infant data suggests that adult-like access to phonological forms is not established in the first two years of life. Taken together, ERPs recorded in word onset priming proved useful in investigating early phonological processing without an explicit behavioral measure.

Phoneme-free prosodic representations are involved in pre-lexical and lexical neurobiological mechanisms underlying spoken word processing.

Recently we reported that spoken stressed and unstressed primes differently modulate Event Related Potentials (ERPs) of spoken initially stressed targets. ERP stress priming was independent of prime-target phoneme overlap. Here we test whether phoneme-free ERP stress priming involves the lexicon. We used German target words with the same onset phonemes but different onset stress, such as MANdel ("almond") and manDAT ("mandate"; capital letters indicate stress). First syllables of those words served as primes. We orthogonally varied prime-target overlap in stress and phonemes. ERP stress priming did neither interact with phoneme priming nor with the stress pattern of the targets. However, polarity of ERP stress priming was reversed to that previously obtained. The present results are evidence for phoneme-free prosodic processing at the lexical level. Together with the previous results they reveal that phoneme-free prosodic representations at the pre-lexical and lexical level are recruited by neurobiological spoken word recognition.

Processing of syllable stress is functionally different from phoneme processing and does not profit from literacy acquisition.

Speech is characterized by phonemes and prosody. Neurocognitive evidence supports the separate processing of each type of information. Therefore, one might suggest individual development of both pathways. In this study, we examine literacy acquisition in middle childhood. Children become aware of the phonemes in speech at that time and refine phoneme processing when they acquire an alphabetic writing system. We test whether an enhanced sensitivity to phonemes in middle childhood extends to other aspects of the speech signal, such as prosody. To investigate prosodic processing, we used stress priming. Spoken stressed and unstressed syllables (primes) preceded spoken German words with stress on the first syllable (targets). We orthogonally varied stress overlap and phoneme overlap between the primes and onsets of the targets. Lexical decisions and Event-Related Potentials (ERPs) for the targets were obtained for pre-reading preschoolers, reading pupils and adults. The behavioral and ERP results were largely comparable across all groups. The fastest responses were observed when the first syllable of the target word shared stress and phonemes with the preceding prime. ERP stress priming and ERP phoneme priming started 200 ms after the target word onset. Bilateral ERP stress priming was characterized by enhanced ERP amplitudes for stress overlap. Left-lateralized ERP phoneme priming replicates previously observed reduced ERP amplitudes for phoneme overlap. Groups differed in the strength of the behavioral phoneme priming and in the late ERP phoneme priming effect. The present results show that enhanced phonological processing in middle childhood is restricted to phonemes and does not extend to prosody. These results are indicative of two parallel processing systems for phonemes and prosody that might follow different developmental trajectories in middle childhood as a function of alphabetic literacy.