This article presents a theoretical framework designed to accommodate core evidence that the abilities to repeat nonwords and to learn the phonological forms of new words are closely linked. Basic findings relating nonword repetition and word learning both in typical samples of children and adults and in individuals with disorders of language learning are described. The theoretical analysis of this evidence is organized around the following claims: first, that nonword repetition and word learning both rely on phonological storage; second, that they are both multiply determined, constrained also by auditory, phonological, and speech–motor output processes; third, that a phonological storage deficit alone may not be sufficient to impair language learning to a substantial degree. It is concluded that word learning mediated by temporary phonological storage is a primitive learning mechanism that is particularly important in the early stages of acquiring a language, but remains available to support word learning across the life span.

In this issue of Applied Psycholinguistics, we present a first annual Keynote Article. The article itself, in this case by Harald Clahsen and Claudia Felser, is followed by the Commentaries of several other researchers. The authors then reply to the Commentaries. It is our hope that this format will provide our readers with an in-depth discussion of central and topical issues in psycholinguistic research. We are grateful to Drs. Clahsen and Felser for writing the initial keynote article as well as to the group of researchers who provided their thoughtful and rigorous commentary.

In this study we examined syntactic ambiguity resolution in two different Chinese languages, Cantonese and Mandarin, which are relatively similar grammatically but very different phonologically. We did this using four-character sentences that could be read using two, two-syllable sequences (2-2) or a structure where the first syllable could be read by itself. The results showed that when both potential readings were semantically congruent, Mandarin speakers had a strong preference for the 2-2 structure and they preferred that structure much more than Cantonese speakers did. We attribute this to Mandarin having a more dominant bisyllabic prosodic foot than Cantonese. When the 2-2 meaning was semantically incongruent, however, the alternative structure was preferred by both Mandarin and Cantonese speakers. Overall, the results suggest that, in silent reading tasks and semantically neutral conditions, the prosodic foot is generated automatically and can affect syntactic choices when ambiguity arises.

The present study investigated whether German speakers compute grammatical gender on the basis of gender-marking regularities. To this purpose two experiments were run. In Experiment 1, participants had to assign the definite article to German nouns in an online task; in the second experiment, participants were confronted with German nouns as well as nonwords in an untimed gender assignment task. In the online experiment, which required the repetition of a visually presented noun with its corresponding definite article as fast as possible, reaction times show that the assignment of the definite determiner to a noun is not facilitated by gender-marking regularities. In an offline gender assignment task, however, participants profited from gender cues during gender assignment to nonwords.

A semantic priming, lexical-decision study was conducted to examine the ability of left- and right-brain damaged individuals to perceive lexical-stress cues and map them onto lexical–semantic representations. Correctly and incorrectly stressed primes were paired with related and unrelated target words to tap implicit processing of lexical prosody. Results conformed with previous studies involving implicit perception of lexical stress, in that the left-hemisphere damaged individuals showed preserved sensitivity to lexical stress patterns as indicated by priming patterns mirroring those of the normal controls. An increased sensitivity to the varying stress patterns of the primes was demonstrated by the right-hemisphere damaged patient group, however. Results are discussed in relation to current theories of prosodic lateralization, with a particular focus on the nature of task demands in lexical stress perception studies.

The ability to process the linguistic input in real time is crucial for successfully acquiring a language, and yet little is known about how language learners comprehend or produce language in real time. Against this background, we have conducted a detailed study of grammatical processing in language learners using experimental psycholinguistic techniques and comparing different populations (mature native speakers, child first language [L1] and adult second language [L2] learners) as well as different domains of language (morphology and syntax). This article presents an overview of the results from this project and of other previous studies, with the aim of explaining how grammatical processing in language learners differs from that of mature native speakers. For child L1 processing, we will argue for a continuity hypothesis claiming that the child's parsing mechanism is basically the same as that of mature speakers and does not change over time. Instead, empirical differences between child and mature speaker's processing can be explained by other factors such as the child's limited working memory capacity and by less efficient lexical retrieval. In nonnative (adult L2) language processing, some striking differences to native speakers were observed in the domain of sentence processing. Adult learners are guided by lexical–semantic cues during parsing in the same way as native speakers, but less so by syntactic information. We suggest that the observed L1/L2 differences can be explained by assuming that the syntactic representations adult L2 learners compute during comprehension are shallower and less detailed than those of native speakers.

The investigation longitudinally examined the phonetic skills of Cypriot-Greek children with late onset of expressive vocabulary. The rate of phonological development within short time increments and the identification of possible speech constraints motivating slow development of expressive language were examined. Participants were seven Cypriot-Greek children identified as late talkers, and seven age-matched normally developing counterparts. Phonetic skills were examined at ages 30, 33, and 36 months for both groups based on spontaneous language samples. Phonological analyses focused on the construction of all subjects' phonetic inventories over time. Both groups exhibited an increase of specific phoneme use over time. Late talkers had significantly poorer phonetic inventories when compared to the control group. Within the experimental group the analysis revealed the persistent omission of word-initial consonants. Results are discussed in terms of language-specific phonological constraints and their relation to slow development of speech.

The assessment of nonword repetition in children goes back at least to 1974, when the Goldman–Fristoe–Woodcock Auditory Skills Battery was published, including a subtest (Sound Mimicry) assessing nonword repetition (Goldman, Fristoe, & Woodcock, 1974). Nevertheless, it was not until 20 years later, when Gathercole and Baddeley (1990) reported a study of short-term memory in children with specific language impairment (SLI), that a theoretical framework was developed linking deficits in nonword repetition to impaired language acquisition. Gathercole's Keynote in this issue (2006) tells the story of how this initial study revealed a striking nonword repetition deficit in children with SLI, complementing work on typically developing children showing a major role of phonological short-term memory (STM) in word learning. As she points out, the story is a complex one: phonological STM is not the only skill tapped by the nonword repetition task, and children may do poorly for different reasons. Furthermore, relationships between nonword repetition and word learning may be reciprocal, with vocabulary level affecting children's ability to segment nonwords efficiently and retain them in memory. However, the original finding, that deficient nonword repetition is a strong correlate of SLI, has stood the test of time, to the extent that poor performance on this test has been used successfully as a marker of a heritable phenotype in molecular genetic studies of SLI (Newbury, Monaco, & Bishop, 2005).

Immigrants' age of arrival (AOA) in a country where a second language (L2) must be learned has consistently been shown to affect the degree of perceived L2 foreign accent. Although the effect of AOA appears strong, AOA is typically correlated with other variables that might influence degree of foreign accent. This study examined the pronunciation of English by native Italian immigrants to Canada who differed in AOA. As in previous research, those who arrived as young adults (late learners) were somewhat older at the time of testing, and produced somewhat longer English sentences, than those who arrived in Canada when they were children (early learners). The results of Experiment 1 showed that the greater chronological age of early than late learners was not responsible for the late learners' stronger foreign accents. Experiment 2 suggested that the late learners' longer L2 sentences were not responsible for observed early–late foreign accent differences. A principle components analysis revealed that variation in AOA and language use, but not chronological age or sentence duration, accounted for a significant amount of variance in the foreign accent ratings. The findings of the study were interpreted to mean that AOA effects on foreign accent are due to the development of the native language phonetic system rather than to maturational constraints on L2 speech learning.

Individual differences in nonword repetition (NWR) show a particularly strong association with vocabulary acquisition for both first- (L1) and second-language (L2) learners, and they serve as a behavioral marker for specific language impairment (SLI) in children (Gathercole, 2006). However, this association is susceptible to alternative explanations.

Clahsen and Felser's article (CF) is an important contribution to the field of psycholinguistics in several respects. First, it draws attention to the importance of a better understanding of the processing mechanisms utilized by child and adult language learners. Differences in these mechanisms may be responsible for the final outcome of the acquisition process. Second, the article provides an excellent summary of current first language (L1) and second language (L2) research on processing. A variety of studies, ranging from morphological off-line investigations to on-line research on syntactic development, are reviewed in a concise and accurate manner; the cross-linguistic dimension of the article makes both the review and the argument even more comprehensive and convincing. Third, based on their own experimental results, and the results from other studies, the authors propose a novel account of L2 processing, the so-called shallow syntax hypothesis (SSH).

To examine interactions between young children's vocabulary size and their phonological abilities, spontaneous language samples were collected from 24-month-olds with precocious lexicons, their age mates (24-month-olds with average-sized lexicons), and their vocabulary mates (30-month-olds with average-sized lexicons). Phonological ability was measured in a variety of ways, such as the number of different consonants that were targeted, the number of different consonants produced correctly, the percentage of consonants produced correctly, and the occurrence of phonological processes. The lexically precocious 24-month-olds were similar to their vocabulary mates on most measures of phonological ability, and both of these groups were generally superior to the 24-month-olds with smaller lexicons. These findings supported a hypothesized relationship between lexicon size and phonological performance, and demonstrated that 2-year-olds' phonological development is more closely related to size of the lexicon than chronological age.

In line with the original presentation of nonword repetition as a measure of phonological short-term memory (Gathercole & Baddeley, 1989), the theoretical account Gathercole (2006) puts forward in her Keynote Article focuses on phonological storage as the key capacity common to nonword repetition and vocabulary acquisition. However, evidence that nonword repetition is influenced by a variety of factors other than item length has led Gathercole to qualify this account. In line with arguments put forward by Snowling, Chiat, and Hulme (1991), one of Gathercole's current claims is that nonword repetition and word learning are constrained by “the quality of temporary storage of phonological representations, and this quality is multiply determined.” Phonological storage is not just a quantity-limited capacity.

Clahsen and Felser (CF) deserve praise for their superlative synthesis of literature relating to grammatical processing, as well as for their original contributions to this area of research. CF “explore the idea that there might be fundamental differences between child L1 and adult L2 processing.” The researchers present evidence that adult second language (L2) processing is often less automatic and less efficient than first language (L1) processing. Qualitative differences are suggested as well. Adult L2 processing may be restricted to shallow computations, whereas L1 processing typically involves detailed representations. These conclusions are reached in large part by comparing highly proficient L2 learners with natives on various neurological and behavioral dimensions of processing. I propose that additional comparisons might be carried out that involve an understudied population: learners whose L2 is their dominant language.

This study investigated the role of phonological memory (PM) in second language (L2) speech production by English-speaking adults who were learning Spanish. PM, operationalized as serial nonword recognition, and L2 lexical, narrative, and grammatical abilities from speech samples were assessed 13 weeks apart. After controlling for the amount of speech output, PM contributed significantly to the development of L2 narrative skills for less proficient participants (17.5% of variance explained) and to gains in correct use of function words for more proficient participants (15.7% of variance explained). These findings suggest that PM plays an important role in narrative development at earlier stages of L2 learning and in the acquisition of grammatical competence at later stages.

To examine effects of input and learner characteristics on morphology acquisition, 60 adult English speakers learned to inflect masculine and feminine Russian nouns in nominative, dative, and genitive cases. By varying training vocabulary size (i.e., type variability), holding constant the number of learning trials, we tested whether learners required a “critical mass” of vocabulary to generalize case marking patterns to new nouns. Cattell's Culture-Fair IQ Test mediated the effect of type variability on success in generalizing case marking to new vocabulary: only participants with above-median Culture-Fair Test scores showed the predicted critical mass effect of better generalization with larger training vocabulary. These results demonstrate how individual differences in central executive functioning and attention allocation capacity can affect adult second language learning.

In her Keynote Article, Gathercole (2006) presents a theoretical framework intended to account for evidence regarding the relation between nonword repetition and word learning. This framework stems from an impressive amount and breadth of research on this topic, including findings from adults and children with typical language abilities as well as language learning disorders. In this commentary we focus on claims relative to the interpretation of nonword repetition deficits in children with specific language impairment (SLI). One issue we address pertains to the nature of the proposed model of nonword processing and word learning, particularly with respect to phonological sensitivity and storage. The second issue we address relates to the assumption that a phonological storage deficit, although not sufficient, is necessary for SLI.

To examine the factors that affect the learning of letter names, an important foundation for literacy, we asked 318 US and 369 Brazilian preschoolers to identify each uppercase letter. Similarity of letter shape was the major determinant of confusion errors in both countries, and children were especially likely to interchange letters that were similar in shape as well as name. Errors were also affected by letter frequency, both general frequency and occurrence of letters in children's own names. Differences in letter names and letter frequencies between English and Portuguese led to certain differences in the patterns of performance for children in the two countries. Other differences appeared to reflect US children's greater familiarity with the conventional order of the alphabet. Boys were overrepresented at the low end of the continuum of letter name knowledge, suggesting that some boys begin formal reading instruction lacking important foundational skills.

Clahsen and Felser (CF) analyze the performance of monolingual children and adult second language (L2) learners in off-line and on-line tasks and compare their performance with that of adult monolinguals. They conclude that child first language (L1) processing is basically the same as adult L1 processing (the contiguity assumption), with differences in performance being due to cognitive developmental limitations. They argue that differences in L2 performance, however, are more qualitative and not explained by shortage of working memory (WM) resources, differences in processing speed, transfer of L1 processing routines, or incomplete acquisition of the target grammar. They propose a shallow structure hypothesis (SSH) to explain the differences reported in sentence processing. According to this, the syntactic representations computed by L2 learners during comprehension are shallower and less detailed than those computed by native speakers and involve more direct form-function mappings.

Choosing appropriate referring expressions requires assessing whether a referent is “available” to the addressee either perceptually or through discourse. In Study 1, we found that 3- and 4-year-olds, but not 2-year-olds, chose different referring expressions (noun vs. pronoun) depending on whether their addressee could see the intended referent or not. In Study 2, in more neutral discourse contexts than previous studies, we found that 3- and 4-year-olds clearly differed in their use of referring expressions according to whether their addressee had already mentioned a referent. Moreover, 2-year-olds responded with more naming constructions when the referent had not been mentioned previously. This suggests that, despite early social–cognitive developments, (a) it takes time to master the given/new contrast linguistically, and (b) children understand the contrast earlier based on discourse, rather than perceptual context.