Poster B15, Tuesday, August 20, 2019, 3:15 – 5:00 pm, Restaurant Hall
How early language development of international adoptees stands the test of time
Gunnar Norrman1;1Stockholm University
Language experience during early childhood shapes linguistic behavior in fundamental ways, but the nature of this interaction and its long-term consequences still elude researchers in the field. Individuals who have been adopted in early childhood and never exposed to their native language again offer a unique opportunity to study long-term effects of early language exposure. Here, we investigated the neural processing of phonological contrasts in adults who were adopted from China to Sweden before the age of 48 months (mean age of adoption 18 +/- 11 months), and who had completely lost any ability to produce or comprehend Chinese. Although data from international adoptees have been used as evidence for neural resetting and re-specialization for the language of adoption (Pallier et al., 2003), recent studies indicate that early experience may have more long-lasting effects under changing circumstances than previously thought (Pierce et al., 2014, 2015). However, although it seems critical, no previous study has examined the processing of phonological contrasts characteristic of the native and the adopted language in the same individuals, and no previous study has addressed this question benefiting from the high temporal resolution of event-related brain potentials. We tested the perception of phonological contrasts unique to either Chinese or Swedish, and compared the adoptees with Chinese and Swedish native speakers with no previous experience of the other language. Stimuli consisted of the combination of a Chinese lexical tone contrast (high-flat and high-rising), and a Swedish vowel contrast (/ʉ/ and /y/). Neural responses were elicited during four blocks of a double deviant oddball task, where each of the four stimuli were presented once in each condition (standard, tone deviant, vowel deviant). Responses were then averaged across condition, and the standard condition subtracted from each deviant condition, to get the event-related difference wave that reflected the cortical response to the unique phonological contrast. Results show significant mismatch negativity (MMN) responses for both conditions (Tone, Vowel), as well as a significant interaction between condition and group (adoptees, Chinese natives, Swedish natives) (F(2,59) = 6.42, p = 0.003, η2 = 0.137). Further analysis reveal significant interactions between group and condition in the Swedish and Chinese natives (F(1,41) = 12.29, p = 0.001, η2 = 0.190), and the Swedish natives and adoptees (F(1,39) = 5.26, p = 0.027, η2 = 0.137), but not in the Chinese natives and the adoptees (F(1,38) = 0.62, p = 0.433, η2 = 0.01). This indicates that while Chinese natives and adoptees differed from Swedish natives in their relative sensitivity to the Chinese and Swedish contrasts, they did not differ from each other. These results show that despite having lost their native language Chinese, and despite being dominant speakers of their second language Swedish, adoptees retain a pattern of early cortical responses to speech similar to that of their native Chinese peers, while differing from native speakers of Swedish. Thus, early language experience leaves long-term traces in neural specialization for speech that persist into adulthood even in the absence of continued exposure to the language of origin.
Themes: Development, Speech Perception
Method: Electrophysiology (MEG/EEG/ECOG)