

Arias-Trejo and Plunkett (2010) concluded that both visual perceptual and semantic similarity (category membership) influenced lexical processing. Furthermore, infants looked away from the target image more quickly if the distractor was perceptually similar to the target. Toddlers looked less at the target image if the distractor image looked perceptually similar and was in the same semantic category, despite parents reporting that their infant understood the words used in the experiment. After the target image was labeled, infants looked more at the target than the distractor image in the first three conditions, but not when the objects were both perceptually and semantically similar. banana), and both perceptually and semantically similar (e.g., dog vs. cookie), perceptually different but semantically similar in that they belonged to the same global category (e.g., apple vs. fish), perceptually similar (objects looked alike) but semantically different (e.g., ball vs. Across conditions the target and distractor image varied with respect to visual perceptual similarity or semantic similarity (category membership) Participants viewed image pairs under four conditions: both perceptually and semantically different (e.g., ball vs. Arias-Trejo and Plunkett (2010) assessed the effects of competition on lexical processing in 18- to 24-month-old toddlers using eye-gaze methods. For example, research with typically developing infants and toddlers demonstrates that perceptual and semantic competition impacts real-time word recognition. 2006), including contexts with competing distractors. Because young children acquire words gradually over time, lexical processing involves both recognizing more words and also becoming more efficient at recognizing the same word in varying contexts ( Fernald et al. Finally, young children, like adults, process speech incrementally as it unfolds ( Marslen-Wilson and Zwitserlood 1989 Fernald et al, 2001, Mahr et al. As early as 18 to 24 months of age, word recognition is influenced by phonologically and semantically related words ( Arias-Trejo and Plunkett 2009 Mani and Plunkett 2010, 2011 Styles and Plunkett 2009), similar to findings from word recognition studies with adults (e.g., McMurray et al. Further, individual differences in efficiency of lexical processing at 18 months predict later language outcomes in typically developing children as well as children at risk for language learning difficulties ( Fernald and Marchman 2012 Marchman and Fernald 2008 Marchman et al. 2006) have demonstrated a dramatic increase in speed and accuracy of spoken word comprehension during the second year of life. Use of eye-gaze methodology, which allows investigators to track eye movements as children look at visual stimuli while listening to spoken language, has been instrumental in advancing this research. On the other hand, there is a considerable amount of research examining lexical processing in typical development. Many children with ASD have delayed vocabulary acquisition, yet we know very little about lexical processing in this group or the mechanisms underlying it. In fact, a number of studies have found that young children with ASD have relatively more severe delays in language comprehension than in language production ( Charman et al. Language comprehension problems are common in children with autism spectrum disorders (ASD).
