Eye-tracking the time‐course of novel word learning and lexical competition in adults and children

Abstract

Lexical competition is a hallmark of proficient, automatic word recognition. Previous research suggests that there is a delay before a new spoken word becomes engaged in this process, with sleep playing an important role. However, data from one method--the visual world paradigm--consistently show competition without a delay. We trained 42 adults and 40 children (aged 7-8) on novel word-object pairings, and employed this paradigm to measure the time-course of lexical competition. Fixations to novel objects upon hearing existing words (e.g., looks to the novel object biscal upon hearing "click on the biscuit") were compared to fixations on untrained objects. Novel word-object pairings learned immediately before testing and those learned the previous day exhibited significant competition effects, with stronger competition for the previous day pairings for children but not adults. Crucially, this competition effect was significantly smaller for novel than existing competitors (e.g., looks to candy upon hearing "click on the candle"), suggesting that novel items may not compete for recognition like fully-fledged lexical items, even after 24 hours. Explicit memory (cued recall) was superior for words learned the day before testing, particularly for children; this effect (but not the lexical competition effects) correlated with sleep-spindle density.Together, the results suggest that different aspects of new word learning follow different time courses: visual world competition effects can emerge swiftly, but are qualitatively different from those observed with established words, and are less reliant upon sleep. Furthermore, the findings fit with the view that word learning earlier in development is boosted by sleep to a greater degree.

Consolidation of vocabulary is associated with sleep in typically developing children, but not in children with dyslexia

“…However, larger overnight increases in lexical competition (as measured by slower responses to existing words, e.g., “dolphin”, once novel competitors have been integrated) were associated with greater spindle power on the night after learning. These data are consistent with findings from adults (Tamminen et al., ; Weighall et al., ) and suggest a degree of constancy in the underlying neurological mechanisms of vocabulary consolidation across development.…”

“…Time spent in each sleep stage (N1, N2, SWS and REM) was calculated, in addition to percent time (relative to total time asleep). Three key parameters were calculated as markers of declarative memory consolidation: spindle density, that is, number of spindles per minute (Tamminen et al., ; Weighall et al., ), spindle power, that is, power density in spindle frequency range (Wilhelm et al., ) and slow wave activity (SWA; Wilhelm et al., , ).…”

“…Spindle density (counts per minute) was then calculated for central (C3, C4) and frontal (F3, F4) EEG channels for each participant and averaged across these channels. Spindle density was averaged across the 12–15 Hz range (following the same procedure as Cairney, Lindsay, Sobczak, Paller, & Gaskell, ; Weighall et al., ).…”

“…Since children display proportionally more SWS than adults, and have stronger slow wave activity (SWA, that is, EEG power in the frequency range of 0.5–4 Hz), peaking at 10–12 years (Campbell & Feinberg, ; Kurth et al., ; Ohayon, Carskadon, Guilleminault, & Vitiello, ), the benefits of sleep for memory consolidation may be enhanced during childhood (James, Gaskell, Weighall, & Henderson, ; Weighall et al., ; Wilhelm et al., ). However, relatively few studies have examined sleep‐associated memory consolidation of declarative memory in children (Backhaus, Hoeckesfeld, Born, Hohagen, & Junghanns, ; Kurdziel et al., ; Prehn‐Kristensen et al., ; Wilhelm et al., , ).…”

“…The main aim of this study was to examine whether individual differences in sleep parameters relate to how well new phonological representations are strengthened and integrated in children with and without dyslexia. Based on previous adult research, we predicted that SWA and sleep spindle power (EEG power density in the slow wave and spindle frequency ranges, respectively) would correlate with overnight improvements in cued recall and overnight increases in lexical competition (Tamminen et al., ; Weighall et al., ). For dyslexics, we predicted poorer novel word learning relative to age‐matched peers, owing to their phonological difficulties (Mayringer & Wimmer, ).…”