Is overt repetition critical to expressive word learning? The role of overt repetition in word learning with and without semantics

Five experiments examined whether overt repetition (i.e., saying a word aloud) during exposure is critical to the expressive learning of new words. When participants did not engage in overt repetition during exposure, they nevertheless exhibited clear expressive learning, both with and without an accompanying semantics, indicating that overt repetition is not critical to expressive word learning. In addition, learning without overt repetition did not differ from learning with overt repetition, suggesting that overt repetition confers no benefit for learning in this situation. These results are discussed in relation to previous studies, and it is suggested that benefits of repetition may accrue primarily in second language rather than in first language word learning. Is the spoken production of new words critical to their expressive learning? That is, can a learner acquire the spoken forms of new words without overtly speaking them? The relevance of this question lies in its implications for understanding of vocabulary acquisition in general, as well as in its implications for methods of vocabulary instruction, which differ in their emphasis on the overt production of new vocabulary material. The answer to the question is not, however, obvious. Indeed, surprisingly little is known definitively about this issue. Suppose, for instance, that a human infant was exposed to two languages that were equally represented in its linguistic environment (say, English and French). In one of the languages (say, French), the infant developed in typical ways, including engaging in linguistic communication receptively (showing comprehension) and expressively (making linguistic utterances). In English, however, the infant engaged only in receptive communication, never speaking. At age 3, would this child have a typical expressive English vocabulary if tested through picture naming © 2008 Cambridge University Press 0142-7164/08 $15.00 Applied Psycholinguistics 29:4 628 Abbs et al.: The role of overt repetition in word learning (e.g., via the Peabody Picture Vocabulary Test; Dunn & Dunn, 1997)? Note that the child would lack neither articulatory skill nor “having language,” because of his/her normal development in French. Demonstration of any expressive vocabulary would indicate that overt production is not an absolute necessity for some expressive vocabulary growth to occur. Any difference in the size of his/her expressive English vocabulary compared with that of peers would presumably be attributable to a lack of overt production of words in English, and would indicate that overt production of words does aid in development of expressive vocabulary. Would the child demonstrate any expressive vocabulary knowledge? Would the size of his/her expressive vocabulary differ from that of peers? The fact that we cannot be sure of the answer to these questions indicates that we do not know what role overt production plays in the expressive learning of spoken words. At least two kinds of overt production can be distinguished, based on the context of production. One type of overt production occurs at the time of exposure to the sound pattern of the word (i.e., to the word form), in the form of immediate repetition. We will term this overt repetition. A second type of overt production is that occurring outside the immediate context of exposure to the word form, as in a spontaneous naming event or an utterance in which the word form is sought out to be used, or in a picture-naming event. We term this overt naming. Here we are concerned with the role in expressive word learning (WL) of the former type of overt production: overt (spoken) repetition. Even with respect to this more limited sense of overt production, it is unclear how crucial it is to WL. If the hypothetical child had never engaged in overt spoken repetition, would s/he be able to engage in overt naming at all? Would the size of his/her expressive vocabulary differ from that of peers? Again, the answer to these questions is not definitively known. Before turning to an examination of theoretical considerations as well as empirical evidence that bear on these questions, let us clarify our usage of the term “word learning.” We adopt an operational definition of expressive WL: we treat it as being measured by the increase in accuracy (over some number of exposures) of overt spoken production of the correct name in a novel name-referent pairing, when cued with the referent, that is, by the increase in accuracy of a particular type of overt naming. We assume that such learning requires, at minimum (a) the establishment of some internal representation of the referent (a semantic representation, which may or may not be very well specified), (b) the establishment of some internal representation of the name (a phonological representation, which must eventually be specified well enough to support spoken production of the name), and (c) the establishment of a link from the former to the latter. In addition, what is manifested as expressive WL very likely involves some facilitation of perceptual processing of the auditory novel name, as well as some facilitation of articulatory processing in production of the novel name. These assumptions are little more than a functional description of what must occur for expressive WL to be manifested; we therefore take these assumptions to be uncontroversial (see also Gupta, 2005). In expressive WL of this type, performance is gauged by production of the phonological word form. Accordingly, the aspect of expressive WL as described Applied Psycholinguistics 29:4 629 Abbs et al.: The role of overt repetition in word learning above that was of primary interest in the present work was the learning of the internal phonological representation. Furthermore, it is particularly in the formation of this phonological representation that the role of repetition has been thought to apply (e.g., Desrochers & Begg, 1987; Ellis & Beaton, 1993; see Gupta, 2005, for additional discussion of expressive WL). The aim of the present work was thus to further clarify the role of repetition, by examining the effect of overt spoken repetition on establishment of the internal phonological representation in expressive WL. Let us further consider the critical independent variable of interest in our examination of overt spoken repetition. To discuss this, it is necessary to provide some information about the experimental design adopted. As just indicated, the dependent measure was performance in an expressive WL task as described above, in which participants received multiple exposures to pairings of novel auditory names with novel visual referents, and were tested on production of the names when cued with the referents. That is, the dependent variable was correct naming performance when cued with the referent. The manipulated variable was whether or not participants were required to overtly repeat the names during exposure trials, that is, whether or not the participants engaged in overt spoken repetition of the names during exposure trials. What are the functional components of performance of overt spoken repetition of a word form? At least two components are clearly identifiable: first, articulatory– phonological planning of the word form must occur. Second, the articulatory– phonological plan must be executed. A critical difference between the experimental condition in which participants perform overt spoken repetition compared with the experimental condition in which participants do not perform overt spoken repetition is this execution of the articulatory–phonological plan. It is important to note here that we expected that participants would engage in internal (silent) repetition, that is, internal rehearsal, in either or both experimental conditions. Evidence for this comes from the work of Papagno, Valentine, and Baddeley (1991), who found that concurrent articulation interfered with learning the pairings of known word forms with novel phonological word forms, but not with other known phonological word forms. This indicated, first, that the locus of the effect of articulatory interference was at phonology, rather than in learning the associative link, and second, that rehearsal, that is, silent internal repetition, was playing a role in the formation of the internal phonological representation. Thus, we expected participants to engage in internal rehearsal in the experimental condition that did not require overt spoken repetition. What is this internal rehearsal? In our view, it can be considered to be articulatory–phonological planning (see, e.g., Gupta & MacWhinney, 1995). But this means that articulatory–phonological planning may be expected to occur in both conditions of our experimental design: both in the condition in which participants perform overt spoken repetition and in the condition in which participants do not perform overt spoken repetition. The critical difference between these two conditions of the experimental design is then the execution of the articulatory– phonological plan. This differentiated the two conditions, and constituted the key independent variable of interest. A finding of significant WL in the no-overt repetition condition would indicate that execution of the articulatory–phonological plan Applied Psycholinguistics 29:4 630 Abbs et al.: The role of overt repetition in word learning is not necessary for learning of the internal phonological representations of word forms. The finding of a difference between WL performance in the two conditions would suggest that execution of the articulatory–phonological plan can play a beneficial role in learning of the internal phonological representation, whether or not it is necessary. Thus, the questions we ask in the present work are (a) whether overt spoken repetition (and in particular, overt execution of the articulatory–phonological plan) is necessary for establishment of the internal phonological representation in expressive WL, and (b) whether overt spoken repetition (overt execution of the articulatory–phonological plan) benefits establishment of the internal phonological representation in expressive WL. In the remainder of this article, we will use the term overt spoken repetition as a shorthand for this critical variable we have discussed, namely, overt execution of the articulatory–phonological plan. In terms of theoretical or a priori considerations, there are reasons to posit as well as deny a role for overt spoken repetition in expressive WL. In contrast, intuition and observation suggest that children do not consistently engage in overt repetition, making it appear unlikely that it could be crucial to expressive WL. The learning of word forms can be conceived of as very similar to the so-called Hebb effect. This effect refers to the finding that when subjects are presented with lists of digits for immediate serial recall, their recall improves for digit lists that, without the participant’s awareness, occur repeatedly, that is, learning of the lists occurs (Hebb, 1961). However, when learning is measured through overt recall of a list, that is an oral response, the effect is dependent on participants’ overt repetition of the lists during presentation (i.e., the opportunity to repeat the entire sequence immediately following presentation), and is not found without this overt repetition (Cunningham, Healy, & Williams, 1984). It has been argued that such learning is analogous to that underlying expressive word form learning: in either case, what is learned expressively is a novel sequence of familiar items: a novel ordering of the phonemes of a language, in the case of word forms, and a novel ordering of digits, in the case of lists (Burgess & Hitch, 2005; Cumming, Page, & Norris, 2003; see also Gupta, Lipinski, Abbs, & Lin, 2005). This would suggest that overt repetition may be critical to word form learning, and hence, to expressive WL. In the language learning literature, evidence regarding the role of repetition is mixed. It has often been suggested that for learning of language as a whole (including not only vocabulary, but also pragmatics, grammar, etc.), rote repetition and memorization is a less effective strategy than more engaging methods, such as spaced recall (Atkinson, 1972; Royer, 1973). Further, the benefit of learning a language in context, such as through immersion, suggests that in comparison, rote memorization is not an effective language-learning tool. However, in secondlanguage learners, evidence suggests that learners who generally dismiss rote memorization strategies as an effective way to learn the overall language still endorse oral, or overt, repetition of a novel phonological form as an effective strategy for learning new words in a language, suggesting a specific role for overt repetition in WL (Gu & Johnson, 1996). In this work, which studied adult Chinese natives who were learning English, Gu and Johnson (1996) found that, in general, the most successful learners eschewed rote repetition in favor of more contextualized approaches for learning a language, but still endorsed overt repetition Applied Psycholinguistics 29:4 631 Abbs et al.: The role of overt repetition in word learning as an effective rehearsal strategy for learning words. Further, this endorsement correlated significantly with a quantitative measure of English proficiency indicating that participants who believed that overt repetition of novel word forms improved their subsequent memory for the word (and were presumably more likely to engage in overt repetition) showed greater linguistic proficiency. This correlational study thus suggests a benefit for overt repetition. Others have also suggested a role for overt repetition in vocabulary acquisition (e.g., Kuhl, 2000; Studdert-Kennedy, 1986). For example, Kuhl and Meltzoff (1982, 1988) suggested that young children resort to a strategy of overt repetition of a heard sequence of phonemes during the period of language acquisition, with the possibility that such repetition may be important to WL. In the few experimental studies that have examined the effectiveness of various rehearsal strategies in WL, overt repetition has been found to facilitate WL, but has not been found to be critical (Duyck, Szmalec, Kemps, & Vandierendonck, 2003; Ellis & Beaton, 1993; Papagno, Valentine, & Baddeley, 1991; Seibert, 1927). These studies found that overtly repeating words during learning is a more effective method for vocabulary acquisition than either silent or visual methods of rehearsal, but the silent and visual methods still showed significant learning. However, these studies focused more on associative learning between foreign language words and native language translation equivalents, and examined what role Baddeley and Hitch’s (1974) phonological loop has in creating this link (but see Duyck et al., 2003, Experiment 2). Further, these studies primarily examined expressive WL in terms of written, rather than spoken response, thus limiting their implications for early WL. Thus, these studies do not provide the strongest test of a critical role for overt repetition in expressive WL. Taken together, the correlational and experimental data presented above provide some evidence for a role of overt repetition in WL. They do not, however, directly examine whether overt repetition is critical to expressive WL and have not always examined auditory presentation of word forms with performance measured through overt naming. The approach in the present investigation is to directly examine the role of overt repetition employing a paradigm in which participants were presented with auditory novel names and visually presented novel referents (rather than definitions or translation equivalents), and asked to learn the names expressively, so that they could subsequently produce the name of each novel referent, when cued with its visual depiction. We focused directly on two questions: (a) Can participants demonstrate expressive WL, in the absence of overt repetition? (b) Does any such demonstrated learning differ from that achieved in the presence of overt repetition?