Developmental continuity in word representation: Infants and adults show parallel effects of phonological mismatch and word familiarity

Are infants' lexical representations structured like adults'? Some recent findings concerning early phonological sensitivity appear consistent with the idea that lexical representations are restructured over development. First, although infants are sensitive to mispronunciations, they have failed to exhibit graded sensitivity to varying degrees of phonological mismatch (e.g. Bailey & Plunkett, 2002). Second, infants' phonological sensitivity depends on their familiarity with the words in which contrasts are embedded (e.g. Fennell & Werker, 2003). This dissertation explores whether the first finding accurately reflects infants' abilities and whether the second finding is unique to infants.; Five experiments assessed infants' and adults' phonological sensitivity during spoken word recognition using eye-tracking. Experiments 1--3 investigated effects of phonological mismatch and word familiarity in 19-month-olds. Infants were presented with pairs of familiar and novel objects; their eye movements were monitored as they heard single-segment onset mispronunciations of familiar words. In Experiment 1, mispronunciations varied in their phonological distance from the target; in Experiment 2, three types of single-feature mispronunciations were compared; in Experiment 3, both phonological distance and word familiarity were manipulated. These experiments demonstrate that under certain referential conditions, infants, like adults, exhibit graded sensitivity to the degree of phonological deviation. No effect of word familiarity was found; however, experimental limitations may have obscured any effects.; Experiments 4 and 5 investigated effects of phonological mismatch and word familiarity in adults. Adults were trained on an artificial lexicon of label-object pairings; their eye-movements were monitored as they heard single-segment onset mispronunciations of the trained labels. Like infants, adults were presented with pairs of familiar (trained) and unfamiliar (untrained) objects during test. Word familiarity was manipulated in both experiments; phonological distance was manipulated across the two experiments. These experiments demonstrate that adults, like infants, are affected by both phonological distance and word familiarity.; These findings suggest that lexical representations are adult-like in structure by 19 months. Moreover, they suggest that effects of word familiarity in infants should not be attributed to immaturities in lexical representations or processing. Parallels between the two populations suggest that there is continuity in the architecture underlying lexical representation and processing throughout development.