Forms of Lexical Knowledge Acquired in a Word Learning Task

Different component processes have been identified in models of lexical access and word production (see Chapter I). The dominant view (Levelt et al., 1999; Caramazza, 1997) is that both semantic and phonological processes are involved. In picture naming, processing o f the pictorial stimulus occurs first (Johnson et al., 1996). Children then draw on information from

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the lemma (semantic representations) and from the lexeme (phonological representations) levels (Levelt et al., 1999). Word learning starts with the reverse flow o f information to that occurring in word production. According to several researchers (Gershkoff-Stowe & Hahn, 2006), an auditory cue provides a basis for the encoding of a phonological representation in memory; activation then spreads to the semantic level where children need to make connections between this novel label and other representations (Booth & Waxman, 2002). The similarity of the component-processes involved in word production and word learning provides a rationale for the choice of tasks used in the current research. These tasks assess the information children possess which is relevant for word production, but also assess children’s general knowledge of the new words such as the information pertinent to a word’s phonological form, semantic properties, or its physical characteristics (see Funnell et al., 2004) for distinction between children’s ability to name novel words and their ability to manifest lexical knowledge about these words).

Assessing lexical knowledge

In the current research, it was decided not only to assess production abilities (i.e. naming) but also other related aspects of lexical knowledge. These include assessments involving children’s receptive abilities (typically assessed by MCTs and where children point to a target or say yes/no to its presence) and expressive abilities (requiring children to provide a name or a definition for the new words; e.g. Kameenui et al., 1982; McKeown et al., 1985). It is believed that both types of measures involve different cognitive processes and place different demands on children’s processing abilities (Nash & Snowling, 2006; Senechal, 1997).

Comprehension merely assesses a child’s ability to recognise an unfamiliar sound pattern

upon hearing its label and then retrieve a mental representation (Gershkoff-Stowe & Hahn, 2006; Huttenlocher, 1974). On the other hand, naming (or the retrieval of words for

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production), requires children to associate its phonological representation with a given meaning. Because fewer cues are available for retrieval (Barsalou, 1999b), production tasks are believed to be more demanding and to require stronger activation (Capone & McGregor, 2005) than tasks involving comprehension. As a result, one would thus expect scores on tests of receptive ability (e.g. lexical decision or comprehension tasks) to be higher than scores on measures of expressive ability (also see Donaldson & Laing, 1993). It was thus decided to include assessments involving both comprehension and production of the target words (see Table 1 for a summary of the main measures of lexical ability used in the current study). Moreover, following the methods used in previous chapters on naming processes (Chapters I to IV), it was also decided to record response times whenever possible. Specifically, measures of speed of response could give an indication of the strength of connections formed during word learning, where stronger connections would be expected to result in quicker, and more accurate, retrieval of information. The analysis of response times is rarely used in developmental approaches of word learning but is nevertheless believed to provide an additional methodological tool for understanding more about lexical knowledge.

Table 1: Measures of lexical knowledge used in the current investigation

Type of task Ability measured

SEMANTIC MCT [receptive]

Definition [offline / expressive] Word knowledge [expressive] Drawing [offline / receptive]

Ability to identify target items by recognizing pictures from a set of visual distracters.

Explicit knowledge of word meanings

Knowledge of general characteristics of target items Knowledge of the visual properties of the target(s)

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PHONOLOGY

Lexical Decision [receptive] Ability to recognize the phonological form (sound structure) of the target word(s) from a set of auditory distracters.

NAMING

Picture naming [expressive] Ability to retrieve the name of novel items for production

1.2. Role of Semantic and Visual Information as Assisting Word Learning

A second issue concerned the effects of visual and semantic input on word learning. As already discussed (see Chapter VI for details), the majority of studies investigating word acquisition have involved the referent being present and the learning situation has often consisted of drawing attention to the association between the phonological label (novel word form) and its referent - e.g. by pointing to the object (Goldin-Meadow, Nusbaum & Kelly, 2001) or contrasting the novel item with a familiar one (Carey & Bartlett’s (1978) instruction about “not the chromium one, the blue one”). Nevertheless, word learning is believed to occur in those situations where the referent is not present (Fischer et al., 1994; Horohov & Oetting, 2004). However, this aspect has rarely been investigated with typical children of school age. In addition, uncertainties remain about the importance of visual information in relation to semantic information because direct comparisons of the effects o f these two input modalities on word learning do not appear to have been made, especially in relation to contexts where the new words are not formally taught. In order to understand more about the effect of visual and of semantic information on word learning, it was decided to manipulate the provision of these two types of contextual inputs.

A useful methodology to examine word learning in older children is the QUIL paradigm developed by Rice and colleagues (Rice, 1989; 1990a & b & c; Rice & Buhr, 1992). It was

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decided to use this experimental paradigm because of its ability to simulate naturalistic learning contexts. As Rice (1990; p. 179) summarised, the QUIL paradigm enables researchers to manipulate the presentation of the information in “careful controlled experimental” conditions. In the current research, the number of exposures of each novel target word remained constant. Perusal of the existing literature showed that there was no consensus on the ‘best’ number of repetitions, though these numbers varied between 4 to 14 (see Table 1 in Chapter VI for details of main QUIL studies) depending on the number of words introduced and the age of the children assessed. Again, according to Rice and colleagues, presentation rate of 5 to 7 for each word (Rice, 1990c; Rice & Woodsmall, 1988) are believed to be a rate consistent with the “rate o f targeted words in educational

programmes” (Rice & Haight, 1986). In the current research, it was therefore decided to

introduce 8 repetitions for each o f the 5 novel words.

This design provides the opportunity to investigate whether semantic input can be as effective as visual input in assisting word learning, as well as whether different sources o f information (semantic vs. visual) affect the different forms o f lexical knowledge and representations that are acquired. Gray (2005) examining 4-5 year olds on a fast mapping task hypothesised that

“different cues may aid different aspects o f word learning” (p. 1452). In this study, children

were in one of two conditions: a semantic condition where information was provided about the object’s superordinate category, function or association (e.g. The haymut was described as

“A kind o f turtle (superordinate), “It crawls (action)” or “I t ’s kind o f like a tortoise

(association)”). On the other hand, children in the phonological condition were provided with information about the sound structure of the target (e.g. “It starts with / h r (initial sound), “It

starts with /h e/’ (initial syllable) or “It rhymes with /hemat/’ (rhyming)). Findings showed

that being given explicit semantic information made a significant difference on the

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comprehension task. In contrast, being given information about the sound structure o f the novel word enhanced subsequent production of the novel words (see also Ralli, 1999; Funnell et al., 2004). From findings such as these, several predictions can be made. One might expect the provision of semantic information in the Speech condition to affect performance in some of the semantic tasks - e.g. definition and word knowledge, because children are given explicit information about the target item. One might also anticipate children in the Speech condition to be at a considerable disadvantage in drawing, naming and/or comprehension as these tasks rely more or less heavily on visual information and children in this condition will not have seen what the object looks like (again, this argument has been put forward by Funnell et al., 2004). On the other hand, if there is cross-modal transfer between different modalities, children in the Speech condition ought to be able to translate this knowledge into different formats.