Lexical–semantic priming effects during infancy

Natalia Arias-Trejo 0 Kim Plunkett () 0 0 Department of Experimental Psychology, University of Oxford , South Parks Road, Oxford OX1 3UD , UK When and how do infants develop a semantic system of words that are related to each other? We investigated word - word associations in early lexical development using an adaptation of the inter-modal preferential looking task where word pairs (as opposed to single target words) were used to direct infants' attention towards a target picture. Two words (prime and target) were presented in quick succession after which infants were presented with a picture pair (target and distracter). Prime - target word pairs were either semantically and associatively related or unrelated; the targets were either named or unnamed. Experiment 1 demonstrated a lexical - semantic priming effect for 21-month olds but not for 18-month olds: unrelated prime words interfered with linguistic target identification for 21-month olds. Follow-up experiments confirmed the interfering effects of unrelated prime words and identified the existence of repetition priming effects as young as 18 months of age. The results of these experiments indicate that infants have begun to develop semantic - associative links between lexical items as early as 21 months of age. - A plethora of studies investigating early lexical development have demonstrated that infants are sensitive to word world associations at least as early as their first birthday (Reznick 1990; Meints et al. 1999; Tincoff & Jusczyk 1999; Schafer 2005; Pruden et al. 2006). These associations form the basis of infants early vocabularies and accumulate rapidly during the second year of life. However, virtually nothing is known about infants knowledge of word word associations which eventually form the basis of the network of meanings underlying the adult semantic system. This study uses the inter-modal preferential looking (IPL) task to investigate whether related words facilitate online lexical processing at 18 and 21 months of age, a crucial period in early word learning. A demonstration of early semantic associative priming effects has the potential to provide a fundamental source of information about the organization of word meaning in the developing lexicon. The rationale of the studies reported here is that related and unrelated words should differentially impact the amount of visual attention that infants direct towards a target image in a preferential looking task. By examining the pattern of priming effects observed for different pairs of words, we aim to identify the structural linkages that bind words together in the infant lexicon and to target when these structures show evidence of emerging. Models of lexical representation assume the existence of an interconnected network. For Fodor (1983), words that frequently co-occur in language (e.g. table chair) form part of this network. Collins & Loftus (1975) proposed a model in which words are organized in a semantic network of interconnected nodes of similar meaning. For instance, the word dog primes the word cat as a consequence of an activation process that spreads across links. In contrast, distributed models of semantic memory (McRae & Boisvert 1998; Cree & McRae 2003) assume that lexical concepts are interconnected owing to their overlap in features (e.g. fur, claws, curvilinear body for cat and dog). Although these models propose different ways by which one concept affects recognition of another, both models consider that properties of concepts are the core of the semantic network. Studies of word associations have demonstrated that prior exposure to a related word facilitates subsequent word processing in adults and school-age children: they are both faster and more accurate if a preceding word is related to a subsequent word (Neely 1991; Nation & Snowling 1999). Although semantic priming effects have been found using nonlinguistic stimuli such as pictures and sounds (Bajo 1988; Ballas 1993; Orgs et al. 2006), in this paper, we focus on linguistic priming effects. Priming effects are typically explored via the lexical decision task (Fischler 1977; Perea & Rosa 2002), the naming task (Thompson-Schill et al. 1998) and occasionally using the event-related potentials technique (Holcomb & Neville 1990; Koivisto & Revonsuo 2001). We propose an adaptation of the IPL task (Golinkoff et al. 1987) to explore early priming effects in infancy. Previous adaptations of this task have been successful at showing effects of prior linguistic or visual information on infants subsequent word object processing (N. AriasTrejo 2005, unpublished doctoral thesis; Styles & Plunkett 2009). A common effect encountered in previous studies is the so-called semantic priming effect (see Neely 1991; Lucas 2000 for reviews) originally reported by Meyer & Schvaneveldt (1971). Adults respond faster and more accurately to a target word that has been immediately preceded by a semantically related prime word. Another effect commonly reported is the associative priming effect where an associative relation between words can facilitate responding to a target, even though the target is semantically unrelated to the prime (Alario et al. 2000; Perea & Rosa 2002; Ferrand & New 2003). While associative relations reflect word use, semantic relations reflect word meaning. However, it is unclear whether semantic or associative relations produce a stronger priming effect. Previous studies with adults have found more reliable priming effects for words that are both semantically and associatively related (e.g. dog cat) than for words that are only semantically (e.g. dog elephant) or associatively (e.g. dog bone) related (Moss et al. 1995; McRae & Boisvert 1998; Perea & Rosa 2002). Perea et al. (1997) failed to find priming effects when category coordinates did not have an associative relation (arm nose), but did find priming effects for related pairs that did not share categorical status (cradle baby), as well as for associatively and categorically related pairs (doctor nurse). In contrast, Perea & Rosa (2002) reported priming effects with synonyms, antonyms and coordinates for pairs that were semantically related but associatively unrelated. Likewise, McRae & Boisvert (1998) suggest that priming effects are not the consequence of mere lexical association, as priming effects are more reliable for non-associated but semantically related words than associatively related words. With the purpose of maximizing the probability of finding early evidence of priming at the level of word meaning, our experiments test word pairs that are both semantically and associatively related according to adult norms (Kiss et al. 1973; Moss & Older 1996). A confluence of different factors, such as stimulus similarity and the timing between prime and target words, are known to modulate priming effects with adults (Holcomb & Neville 1990; Anderson & Holcomb 1995; Perea & Rosa 2002). There is a general co (...truncated)