The development of English vowel perception in monolingual and bilingual infants: Neurophysiological correlates

Abstract

The goal of this paper was to examine intrinsic and extrinsic factors contributing to the development of speech perception in monolingual and bilingual infants and toddlers. A substantial number of behavioral studies have characterized when infants show changes in behavior towards speech sounds in relation to amount of experience with these sounds. However, these studies cannot explain to what extent the developmental timeline is influenced by experience with the language versus constraints imposed by cortical maturation. Studies using electrophysiological measures to examine the development of auditory and speech processing have shown great differences in infant and adult electrophysiological correlates of processing. Many of these differences are a function of immature cortex in the infant. In this paper, we examined the maturation of infant and child event-related-potential (ERP) electrophysiological components in processing an English vowel contrast and explored to what extent these components are influenced by intrinsic (e.g., sex) versus extrinsic factors, such as language experience (monolingual vs. bilingual). Our findings demonstrate differences in the pattern of ERP responses related to age and sex, as well as language experience. These differences make it clear that general maturational factors need to be taken into consideration in examining the effect of language experience on the neurodevelopment of speech perception.

The Development of Mismatch Responses to Mandarin Lexical Tones in Early Infancy

“…However, no preceding MMN was found in the P-MMRs elicited by T1/T3 in newborns or by T2/T3 in 6-month-old infants. This is in line with the study conducted by Shafer et al (2011), which reported a P-MMR to English vowel contrasts without preceding MMN from 6 to 18 months of age. The P-MMR may not merely reflect the involuntary attention shifting as the P3a, but also indexes a preliminary change detection mechanism in infancy.…”

“…The waking infants were seated comfortably on their caregivers' laps. In following similar procedures that have been used in other infant MMN studies (Morr et al, 2002;Shafer, Yu, & Datta, 2011), silent movies or cartoons were played on a monitor in front of the waking infants to engage them and minimize their movement. An experimenter entertained the infants with quiet toys whenever they lost interest in the videos.…”

Bilingualism and increased attention to speech: Evidence from event-related potentials

“…Although our P2 window clearly falls outside the P1 time-window (Fig. 1), auditory P1 latencies in response to vowels have been reported to extend into our P2 time-window (Shafer et al, 2011). However, other studies using spoken word stimuli observed similar P1 latencies as here (100 ms; Mills & Sheehan, 2007).…”

“…ERP components can be roughly divided into early components reflecting perceptual processes modulated by attention (up to $300 ms after stimulus onset), and later components reflecting more conscious stimulus processing influenced by voluntary allocation of attention and cognitive strategies ($300-600 ms after stimulus onset). Importantly, studies of early ERPs in response to (speech) sounds have shown that maturation of the auditory cortex is directly liked to language learning and that the rate of maturation differs in monolingual and bilingual children (Kuhl et al, 2008;Shafer, Yu, & Datta, 2011).…”

Mismatch Negativity (MMN) as an Index of Cognitive Dysfunction

“…This may be a developmental issue. The negative MMR may be equivalent to the adult MMN (He et al 2007, 2009; Shafer et al 2010, 2011). With increasing age, the negative MMR becomes larger in amplitude and earlier in latency (Shafer et al 2000, 2010; Morr et al 2002).…”