Consonant and Vowel Processing in Word Form Segmentation: An Infant ERP Study

Abstract

Segmentation skill and the preferential processing of consonants (C-bias) develop during the second half of the first year of life and it has been proposed that these facilitate language acquisition. We used Event-related brain potentials (ERPs) to investigate the neural bases of early word form segmentation, and of the early processing of onset consonants, medial vowels, and coda consonants, exploring how differences in these early skills might be related to later language outcomes. Our results with French-learning eight-month-old infants primarily support previous studies that found that the word familiarity effect in segmentation is developing from a positive to a negative polarity at this age. Although as a group infants exhibited an anterior-localized negative effect, inspection of individual results revealed that a majority of infants showed a negative-going response (Negative Responders), while a minority showed a positive-going response (Positive Responders). Furthermore, all infants demonstrated sensitivity to onset consonant mispronunciations, while Negative Responders demonstrated a lack of sensitivity to vowel mispronunciations, a developmental pattern similar to previous literature. Responses to coda consonant mispronunciations revealed neither sensitivity nor lack of sensitivity. We found that infants showing a more mature, negative response to newly segmented words compared to control words (evaluating segmentation skill) and mispronunciations (evaluating phonological processing) at test also had greater growth in word production over the second year of life than infants showing a more positive response. These results establish a relationship between early segmentation skills and phonological processing (not modulated by the type of mispronunciation) and later lexical skills.

Keywords: Event-related brain potentials (ERPs); French-learning infants; consonant bias; individual variability; lexical processing; word form segmentation.

Figure 1

Position of electrodes included in final event-related potentials (ERP) data analysis. Electrodes highlighted in red represent left and right anterior electrodes, in black left and right central electrodes, and in striped red and black left and right posterior electrodes.

Figure 2

(a) Grand-average event-related potentials (ERP) responses time-locked to word onset for the first two (1st/2nd) and last two (7th/8th) tokens of the embedded target words in the Familiarization Phase for the 6 ROIs: left anterior (LA), right anterior (RA), left central (LC), right central (LR), left posterior (LP), right posterior (RP). The time windows of interest, 180–350 ms and 600–850 ms are highlighted in gray. (b) Mean distribution plots for the ERP effect of memory trace formation in the Familiarization Phase (7th/8th tokens—1st/2nd) in the 180–350 ms time window for overall group performance (left), Negative Responders (central), and Positive Responders (right).

Figure 3

(a) Grand-average event-related potentials (ERP) responses time-locked to word onset for the target and control words presented in the Test Phase for the 6 ROIs: left anterior (LA), right anterior (RA), left central (LC), right central (LR), left posterior (LP), right posterior (RP). The time window of interest, 200–500 ms is highlighted in gray and significant effects are marked as * p < 0.05. (b) Mean distribution plots for the ERP effect of word familiarity in the Test Phase (target—control words) in the 200–500 ms time window for overall group performance (left), Negative Responders (central), and Positive Responders (right).

Figure 4

Total word production (z-score) at the four ages measures (8, 13, 16, 24 months) for both Negative and Positive Responders. Lines indicate the fit of the model and whiskers indicate a standard error of 1.

Figure 5

(a) Grand-average event-related potentials (ERP) responses time-locked to word onset for target words and onset consonant mispronunciations in the Test Phase for the 6 ROIs: left anterior (LA), right anterior (RA), left central (LC), right central (LR), left posterior (LP), right posterior (RP). The time windows of interest, 200–320 ms and 550 to 700 ms are highlighted in gray. (b) Mean distribution plots for the ERP effect of mispronunciation sensitivity in the Test Phase (target words—onset consonant mispronunciations) in the 200–320 ms time window for overall group performance (left), Negative Responders (central), and Positive Responders (right).

Figure 6

(a) Grand-average event-related potentials (ERP) responses time-locked to word onset for target words and medial vowel mispronunciations in the Test Phase for the 6 ROIs: left anterior (LA), right anterior (RA), left central (LC), right central (LR), left posterior (LP), right posterior (RP). The time window of interest, 200–320 ms is highlighted in gray. (b) Mean distribution plots for the ERP effect of mispronunciation sensitivity in the Test Phase (target words—medial vowel mispronunciations) in the 200–320 ms time window for overall group performance (left), Negative Responders (central), and Positive Responders (right).

Figure 7

(a) Grand-average event-related potentials ERP responses time-locked to word onset for target words and coda consonant mispronunciations in the Test Phase for the 6 ROIs: left anterior (LA), right anterior (RA), left central (LC), right central (LR), left posterior (LP), right posterior (RP). The time window of interest, 200–400 ms is highlighted in gray. (b) Mean distribution plots for the ERP effect of mispronunciation sensitivity in the Test Phase (target words—coda consonant mispronunciations) in the 200–320 ms time window for overall group performance (left), Negative Responders (central), and Positive Responders (right).

Figure 8

Total word production (z-score) at the four ages measures (8, 13, 16, 24 months) as a function of the mispronunciation sensitivity difference score (target—mispronunciation) at eight months. Participants were grouped into whether this difference score was greater than 1 SD below the group mean (More Negative), within 1 SD of the mean (Mean), or greater than 1 SD above (More Positive). Note that these data groupings by mispronunciation difference score is merely for illustrative purposes, the predictor in the model was continuous. Lines indicate the fit of the model and whiskers indicate a standard error of 1.