2.1 Word Exposure Frequency and Vocabulary Learning
Vocabulary acquisition has been traditionally considered central to second language learning. Rivers (1983) states that it is vocabulary, rather than grammar, that is needed to get meaning across in basic communicative competence contexts, and McCarthy (1990) suggests that it is words, independently of grammar or syntax, that conveys meaning and therefore communicate ideas. As Chambers (1999) points out, vocabulary learning is sine qua non to language learning, without which communication is bound to be unsuccessful (Vermeer, 1992). More recent studies suggest that second language learning is largely dependent on vocabulary (Restrepo Ramos, 2015) and that ‘[l]earners need large vocabularies to successfully use a second language, and so high vocabulary targets need to be set and pursued’ (Schmitt, 2008, p. 353). Learning has often been explained in relation to the number of times a second-language learner encounters any given word. In line with this, Mason and Krashen (1997) and Grabe and Stoller (1997) state that exposure to vocabulary leads to language learning. Also, Meara (1992) developed a model for English as a Second Language vocabulary testing in which vocabulary growth correlated with general frequency of occurrence, establishing a distinction between high-frequency and low-frequency words. Milton endorses Meara’s frequency model of learning and claims that, as a general rule, ‘the more frequent a word is, the more likely it is to be learned’ (2009, p. 26), which is supported by recent studies suggesting that ‘[v]ocabulary learning occurs over time and is dependent on learner actions and on multiple encounters with a given item’ (Godwin-Jones, 2018, p. 1).
However, while general word exposure frequency is assumed to bear an impact on L2 vocabulary gains, there seems to be no consensus on the number of times a word needs to appear before it is assimilated. Saragi, Nation and Meister (1978) and Rott (1999) state that a word is learnt after six encounters. Jenkins, Stein and Wysocki (1984) identified that 25% of the learners in their study acquired a word after it had been encountered ten times, whereas Herman, Anderson, Pearson, and Nagy (1987) indicate that full acquisition of word occurs after 20 encounters. Regarding DGBL contexts, Chen and Hsu (2019, p. 11) believe that ‘repetitive exposure (i.e. more than six times) to words also has a positive influence on incremental vocabulary acquisition in gaming’. However, as Nation and Gu (2007) indicate, not all words are learnt the same way. Ellis and Beaton (1993) state that nouns and adjectives are easier to learn than verbs and adverbs, whereas Laufer (1990) identifies a series of ‘intralexical factors’ related to form and meaning stemming from the word itself which may facilitate or hamper the learnability of lexical items, namely pronounceability, orthography, length, morphology, similarity of lexical forms, grammar, and semantic features. In fact, recent studies suggest that other factors like saliency (the relevance of a word within a given context) and distribution (the way occurrences are distributed over time) may actually have a greater impact on L2 vocabulary learning processes than frequency (Alcaraz-Mármol, 2010, 2015).