From cat to dog: Investigating organisation in the infant lexicon

Do infants learn their early words in isolation? Or do they integrate new words into an inter-connected semantic system? Between the ages of one and two, infants develop a prodigious word-learning ability (P. Bloom, 2002; Fenson et al., 1994; Hamilton et al., 2000). Little is known, however, about how and when infants integrate their accumulating word-knowledge into an adult-like lexical network – one sensitive to relationships such as association and semantic category organisation. For adults, context has a strong effect on the ease and speed of linguistic processing, and on behavioural responses to language. In lexical priming studies, both visual and auditory context are known to influence the speed of lexical processing (Antos, 1979; Meyer & Schvaneveldt, 1971; Radeau, 1983) and ambiguity resolution (Swinney, 1979), as well as guide predictive looks to contextually relevant areas of a complex scene (Huettig & McQueen, 2007; Kamide et al., 2001). And while priming studies have been conducted with children (Betjemann & Keenan, 2008; Duncan & Kellas, 1983; Hartfield & Conture, 2006; Hashimoto et al., 2007; McCauley et al., 1976; Nation & Snowling, 1999; Radeau, 1983; Schvaneveldt et al., 1977) and toddlers (Krackow & Gordon, 1998), the currently available methods are not applicable below the age of three. This thesis presents a body of research which combines two experimental paradigms into a single new method which allows investigation of relationships within the developing infant lexicon. Over a series of experiments, this thesis develops a version of the infant-friendly Inter-modal Preferential Looking (IPL) task within the lexical priming paradigm. The method combines fine-grained temporal sensitivity with an intuitive, infant-friendly task. Priming effects were observed during lexical access for children two years-of-age and older, providing a promising new direction for investigations into the development of semantic organisation during development.