This article presents a theoretical review of and methodological guidelines for the study of two key notions in second language acquisition research, complexity and difficulty. The term "complexity" has gained considerable currency over the past decades and has taken on a wide range of meanings. We argue for a more restricted…

Successful language use requires the ability to process nonadjacent dependencies (NADs) that occur in linguistic input. Learning such structural regularities seems therefore crucial for children, and researchers have indeed proposed that language problems in children with developmental language disorder (DLD), especially problems with grammar, are…

Multilingual research could offer a unique perspective on how the languages already acquired by a person affect the online processing of a new language. But it is currently difficult to assess this issue because theoretical accounts of multilingualism have focused on acquisition rather than processing and most empirical research to date has…

Native speakers strongly disprefer novel formulations when a conventional alternative expresses the same intended message, presumably because the more conventional form competes with the novel form. In five studies, second language (L2) speakers were less influenced by competing alternatives than native speakers. L2 speakers accepted novel…

The "Common European Framework of Reference" (CEFR) is the most widespread reference tool for linking language tests, curricula, and national educational standards to levels of foreign language proficiency in Europe. In spite of this, little is known about how the CEFR levels (A1-C2) relate to empirical learner language(s). This article…

When native speakers judge the acceptability of novel sentences, they appear to implicitly take competing formulations into account, judging novel sentences with a readily available alternative formulation to be less acceptable than novel sentences with no competing alternative. Moreover, novel sentences with a competing alternative are more…

The range, variety, or diversity of words found in learners' language use is believed to reflect the complexity of their vocabulary knowledge as well as the level of their language proficiency. Many indices of lexical diversity have been proposed, most of which involve statistical relationships between types and tokens, and which ultimately…

This study examines whether adult second language (L2) learners of an ungendered first language (L1) are sensitive to gender congruency (grammatical feature absent in the L1) and noun animacy (semantic feature present in the L1) when processing L2 gender concord and whether L2 proficiency level determines such sensitivity. To address these…

This article compares the effects of listening and reading on the incidental acquisition and retention of vocabulary. Two hundred thirty students participated in the study: They either (a) read three academic texts, (b) watched three lectures, or (c) received no input at all and just completed the vocabulary measures. This study also assessed and…

Although research has consistently shown that a bilingual's two languages interact on multiple levels, it is also well-established that bilinguals can vary considerably in their proficiency in the second language (L2). In this paper we review empirical studies that have examined how differences in L2 proficiency modulate cross-language…

Learning inflectional morphology is a vexing problem for second language (L2) learners. Children acquiring their native language also experience some difficulty, which results in their committing overgeneralization errors. Long after individuals have achieved a high level of proficiency in the L2, they are still plagued by uncertainty when it…

Given that this special issue is devoted to the acquisition and processing of inflectional morphology by second language (L2) learners, the question in the title may appear redundant. However, recent research on first language (L1) and L2 morphological processing has challenged basic assumptions about the status of inflectional morphology in…

This longitudinal study investigates the development of writing proficiency in English as a foreign language (EFL), in contrast to the development of first language (L1) writing proficiency in Dutch L1, in a sample of almost 400 secondary school students in the Netherlands. Students performed several writing tasks in both languages in three…

With Chinese native-speaker data as the baseline, this study investigates the use of the morphosyntactic particle DE by learners of Chinese as a second language. The general patterns are as follows: (a) DE tends to be deleted more in informal speech than in formal settings; (b) higher proficiency and longer residence in China--more interactions…

This article analyzes whether the distribution of the hours of classroom practice has any effect on students' foreign language gains by comparing two types of EFL (English as a foreign language) programs: one in which the hours of instruction are distributed in long sessions over a short period (intensive course) and another in which the students…