Individual differences in lexical processing efficiency and vocabulary in toddlers: A longitudinal investigation

Abstract

Research on infants' online lexical processing by Fernald, Perfors, and Marchman (2006) revealed substantial individual differences that are related to vocabulary development, such that infants with better lexical processing efficiency show greater vocabulary growth across time. Although it is clear that individual differences in lexical processing efficiency exist and are meaningful, the theoretical nature of lexical processing efficiency and its relation to vocabulary size is less clear. In the current study, we asked two questions: (a) Is lexical processing efficiency better conceptualized as a central processing capacity or as an emergent capacity reflecting a collection of word-specific capacities? and (b) Is there evidence for a causal role for lexical processing efficiency in early vocabulary development? In the study, 120 infants were tested on a measure of lexical processing at 18, 21, and 24 months, and their vocabulary was measured via parent report. Structural equation modeling of the 18-month time point data revealed that both theoretical constructs represented in the first question above (a) fit the data. A set of regression analyses on the longitudinal data revealed little evidence for a causal effect of lexical processing on vocabulary but revealed a significant effect of vocabulary size on lexical processing

The Longitudinal Relationship Between Conversational Turn‐Taking and Vocabulary Growth in Early Language Development

“…Since socioeconomic status (SES) has been shown to be associated with both variation in input and vocabulary development (Bergelson et al, 2019; Hart & Risley, 1995; Hoff, 2003; Rowe, 2012), it is important to acknowledge that our results may not generalize fully to other populations. Interestingly, however, we note that even within more narrow SES bands we see large individual differences in both input and vocabulary development (Donnelly & Kidd, 2020; Weisleder & Fernald, 2013). Data on participant ethnicity were not collected, although the sample was representative of the Canberra population, which is predominantly of white, Anglo‐Celtic origin (approx.…”

Onset Neighborhood Density Slows Lexical Access in High Vocabulary 30‐Month Olds

“…RTs were calculated following the procedure from Fernald, Perfors, and Marchman (2006): On the trials in which participants were looking to the distracter image prior to the onset of the target word, we calculated the duration between the onset of the target word and the participant's first 100 ms fixation on the target between 200 and 1800 ms post onset. While previous research has extracted RTs after 300 ms, these studies have typically been done with younger children (Donnelly & Kidd, 2020; Fernald et al., 2006), and we found that doing so dropped an unacceptable number of trials (347 trials or 25% of possible trials, compared to 171% or 12% of possible trials when 200 ms was used). The proportion of looks to the target image was calculated after the onset of the target word.…”

“…Taken with these findings, our results place an important constraint on the large current research focused on lexical processing as a predictor of individual differences in language outcomes (e.g., Egger, Rowland, & Bergmann, 2020; Fernald et al., 2006; Marchman & Fernald, 2008). An important conceptual limitation of this work is that it is conducted largely without a working theoretical model of the lexicon (see Donnelly & Kidd, 2020); it implicitly assumes a largely unidirectional and linear relationship between knowledge and lexical processing speed (i.e., faster RTs are always better). Our results, as well as the literature described above, indicate that there are subtle item‐based influences on lexical access that are inconsistent with this assumption but which fit with what we know about adult lexical access.…”

“…This may reflect the limitations of using proportions as a dependent variable for this age group. While proportions are commonly used in the LWL task at a young age (Lany, Giglio, & Oswalt, 2018), given that the RTs on the LWL task decrease with age (Donnelly & Kidd, 2020; Fernald et al., 1998; Fernald et al., 2006), proportions may become less reliable as they are affected by where the participant looks after fixating on the target word. This is consistent with the fact that Mani and Plunkett (2011) and Angulo‐Chavira and Arias‐Trejo (2018) found that phonological primes had the opposite effect on the proportion of looks to target in a preferential looking task (see also Avila‐Varela et al., 2021).…”

“…Data came from a cohort of children who are being followed as part of a larger longitudinal project tracking the interaction between language processing and language development from 9 months to 5 years (see Donnelly & Kidd, 2020; Kidd, Junge, Spokes, Morrison, & Cutler, 2018). Families were recruited from Canberra, a medium‐sized city in Australia.…”