While children appear to learn words from incidental exposure alone (Nation, 2001; Swanborn & de Glopper, 1999), deliberate or ‘explicit’ instruction in word meaning is also shown to be a pow- erful source of novel vocabulary acquisition: indeed, meta-analyses support the responsiveness of vocabulary knowledge to explicit instruction, showing a wide range of methods (or combina- tions thereof) to be effective for young word learners (Elleman, Lindo, Morphy & Compton, 2009; Elleman, Steacy, Olinghouse & Compton, 2017; Hairrell, Rupley & Simmons, 2011; Marulis & Neuman, 2010; Stahl & Fairbanks, 1986; Wright & Cervetti, 2017).
Early research in vocabulary instruction sought to compare the efficacy of definitional and con- textual approaches to the acquisition and retention of word knowledge. A definitional approach is one in which word meanings are conveyed explicitly in the form of traditional definitions, while a contextual approach places emphasis upon contextual cues, typically by placing novel words within sentences or passages (Stahl & Fairbanks, 1986). In a meta-analysis of 52 studies involv- ing participants of kindergarten to college age, Stahl and Fairbanks (1986) contrasted vocabulary instruction programmes with a definitional or contextual emphasis, as well as those with a bal- ance between the two. The review firstly looked at the influence of teaching style on vocabulary knowledge in and of itself, and found that all types of approaches were found to result in large and statistically significant improvements (d = 0.76 to 2.36). However, when assessing the influ- ence of teaching style on children’s passage comprehension skill, the review found that methods with a balanced approach or definitional emphasis were the only ones to result in significant im- provements (d = 1.40 and 0.76, respectively). Thus, results suggested that all forms of instruction were successful in improving vocabulary knowledge itself, but that a combination of definitional and contextual information may serve to best promote reading comprehension. Similarly, a more recent meta-analysis of 64 vocabulary instruction studies by Marulis and Neuman (2010) found that young monolingual learners up to age 6 benefited significantly more from definition-only or combined definition-and-context methods as compared with context-only methods. However, it should be noted that the studies in this latter review are likely to have targeted knowledge of fairly simple, concrete vocabulary for children of kindergarten age and therefore may lack direct com- parison to vocabulary instruction in older children, which may involve more abstract vocabulary presented in longer and more detailed contexts (e.g. McKeown, Beck, Omanson & Perfetti, 1983; Snow, Lawrence & White, 2009).
Nash and Snowling (2006) compared definitional and contextual approaches to vocabulary instruction with a sample of 24 Year 3 pupils (aged 7 to 8 years) in England. After the screen- ing of an entire Year 3 cohort (n=71), those children who scored in the bottom third in receptive vocabulary (BPVS-II, Dunn, Dunn, Whetton & Burley, 1997) and/or a composite measure of vo-
cabulary and narrative (Expression, Reception and Recall of Narrative Instrument, Bishop, 2004) were selected to take part and randomly allocated to either a definition or context condition. All children received two 30-minute teaching sessions once a week for six weeks, covering two words per session. Activities in the definition condition included work on simplified definitions, links to personal experiences, spelling, and recall, whereas children in the context condition read short bespoke passages containing target words and cues and then filled in semantic maps. Although both groups made gains in word knowledge at immediate post-test, the only statistically signifi- cant difference was the relatively higher performance of the children in the context condition on a bespoke verbal definitions outcome measure at delayed 3-month post-test. According to the au- thors, work with passages in the context condition may have been more enjoyable and interactive for children, and the appearance of target words alongside other important semantic, syntactic, and pragmatic information may have resulted in improved ability to give a definition.
Wilkinson and Houston-Price (2013) experimentally manipulated definitional and contextual constraints to investigate word learning outcomes in a sample of 165 monolingual children in two age groups (7 and 9 year-olds). In whole class settings, pupils learned target words which appeared in the BPVS-II using one of two approaches: in a definition condition, words were presented in context either with or without a definition, and in a context condition words were pre- sented in context either three times in the same story, or three times in different stories. Note that all conditions included some form of context in which target words were presented within written passages. Receptive vocabulary knowledge, as measured by knowledge of target and control words from the BPVS-II, was assessed at baseline and at two time points following the end of the teaching (t1 and t2). Although all children showed significant gains in vocabulary knowledge by t1, and retained this at t2, performance on the BPVS indicates only receptive knowledge, in contrast to Nash and Snowling (2006) who also included an expressive outcome measure, and therefore it is unknown to what extent the children acquired additional aspects of word meaning, such as their function (Nation, 2001; Section 5.1). Crucially in this study, however, the addition of a definition resulted in significantly larger gains in word learning, whereas no differences were observed between the two context conditions. Thus, it would appear that the provision of explicit information relating to word meaning was more facilitative of novel word learning than varying the contexts in which words appeared. It should be noted that prior vocabulary knowledge (as mea- sured by baseline BPVS-II raw scores) accounted for 24% of variance in word learning at t1 and a similar amount at t2, supporting the role of prior knowledge in acquisition of novel vocabulary. The results of this study support the role of definitions in word learning but are less conclusive with regard to the role of context, showing no significant differences when words were presented within the same story or across different stories.
In summary, while there is general support for the effectiveness of definitions in vocabulary in- struction studies with monolingual learners, the importance of context should not be downplayed, as this is also shown to result in gains in knowledge. The complementary roles of definitional and contextual information may be expected to result in positive instructional outcomes, given that vocabulary knowledge is conceptualised as multidimensional and consisting of not only meaning, but also of form and function (Section 2.1.2). Importantly, the way in which vocabulary knowledge is measured may reveal subtle differences in children’s performance according to having received definitional or contextual instruction, i.e. awarding points for contextual information about a tar-
get word or for its correct use within a sentence (this issue is returned to in Section 6.9.1). The following section will consider key considerations in the design and implementation of vocabulary intervention studies based on work with monolingual learners.