The Role of Contextual Repetition During Fast Mapping on Word Learning

The Role of Contextual Repetition During Fast Mapping on Word Learning Emma L. Axelsson (e.axelsson@unsw.edu.au) School of Psychiatry, ICAMHS Research, Mental Health Centre Level 1, Locked Bag 7103 Liverpool Hospital, Liverpool BC NSW 1871 AUSTRALIA Jessica S. Horst (jessica@sussex.ac.uk) School of Psychology, Pevensey 1 Building Falmer, Brighton, BN1 9QH, UK Abstract Recent research suggests that children’s ability to learn words via fast mapping is strongly related to the attentional demands of the task. Here we explore whether lowering the attentional demands during the initial fast mapping task facilitates word learning. Three-year-old children completed fast mapping and test trials using a touch screen computer. For half of the children, the non-targets (competitors) repeated across trials and for other children there was no repetition. All children received the same word learning test trials. Only children who had received repeating competitors (lower attentional demands) during the initial fast mapping task demonstrated word learning. Thus, these data suggest that children’s ability to learn novel names is strongly influenced by the competition and attentional demands of the initial fast mapping context. Keywords: fast mapping; word learning; competition; attentional demands. Does Fast Mapping Enable Word Learning? Learning to comprehend the vast number of words that children are bombarded with daily is a daunting task. Arguably, it is equally daunting for researchers to explain the mechanisms responsible for children’s developing ability to understand what a speaker is referring to when uttering a new word, but also children’s ability to remember the link between the word and referent for later encounters. Without direct instruction, children effectively determine the referent for a novel word on their own—particularly when the referent is presented in the context of known objects. Typically referred to as fast mapping (Carey, 1978), children appear to determine the referent via process-of- elimination (Halberda, 2003). That is, children use their prior knowledge (i.e., known vocabulary) to rule out the objects they have already linked to a name. Instead, they select a novel object as the likely referent of a novel name. Biases to novelty appear to be key in fast mapping. Recent research further indicates that even in the context of other nameless, novel objects, children will select the most novel object as a referent for a novel name (Horst, Samuelson, Kucker, & McMurray, 2011; Mather & Plunkett, 2012). However, fast mapping is not word learning per se, but rather an initial step in the word learning process (Carey, 1978; Horst & Samuelson, 2008). Fast mapping appears to be relatively easy for children, yet retention of the name- object mappings is more difficult. For example, Horst and Samuelson (2008) presented 24-month-old children with referent selection (i.e., fast mapping) trials with one novel object and two known objects. Only 5 minutes later, they tested children’s retention for the same novel name-object associations by presenting the targets among other novel targets that had been encountered during the initial referent selection trials and foils that had been seen during a preferential looking task. Children had little difficulty selecting the correct referents on the initial referent selection trials. However, children performed at chance levels on the retention trials, suggesting that the initial name-object mappings did not lead to robust representations in long-term memory. Other studies have found similar difficulties in long-term retention of name-object mappings despite demonstrations of minimal difficulty disambiguating novel from known objects (e.g., Bion, Borovsky & Fernald, 2013; Gureen, Horne & Erjavec, 2012). Note, other studies do suggest minimal exposure to a novel word and object may lead to long-term retention of the association, but these have typically involved only naming a single novel object (e.g., Woodward et al., 1994). It remains unclear, therefore, whether children’s selection of the target on the delayed test trials are really in response to the specific phonetic content of the new word or because that word was the only new word introduced during training, rendering it unique among the available alternatives (Dollaghan, 1985; Schafer & Plunkett, 1998). Task Demands Taken together, these studies suggest that children are adept at forming the initial associations between novel referents and their names, however, children’s ability to retain these mappings may suffer when task demands are high. For example, in a recent study exploring the effect of the number of known competitors present during the initial fast mapping task on subsequent word learning, 2-year-old children were only able to retain novel name-object associations when task demands were relatively low (Horst, Scott & Pollard, 2010). Specifically, children were only able to retain words when they had seen few known competitors across fast mapping trials (eight) but not when they had seen more competitors across trials (12 or 15)—although the number of targets was the same for all groups. Clearly then, the non-target competitors play an important role in word learning via fast mapping. Horst and Samuelson (2008) found that children could only retain the novel name-object associations when ostensive naming was