The effect of age of acquisition, socioeducational status, and proficiency on the neural processing of second language speech sounds

Abstract

This study investigates the role of age of acquisition (AoA), socioeducational status (SES), and second language (L2) proficiency on the neural processing of L2 speech sounds. In a task of pre-attentive listening and passive viewing, Spanish-English bilinguals and a control group of English monolinguals listened to English syllables while watching a film of natural scenery. Eight regions of interest were selected from brain areas involved in speech perception and executive processes. The regions of interest were examined in 2 separate two-way ANOVA (AoA×SES; AoA×L2 proficiency). The results showed that AoA was the main variable affecting the neural response in L2 speech processing. Direct comparisons between AoA groups of equivalent SES and proficiency level enhanced the intensity and magnitude of the results. These results suggest that AoA, more than SES and proficiency level, determines which brain regions are recruited for the processing of second language speech sounds.

Keywords: Bilingualism; Development; Language; Neuroscience; Perception; Speech.

Figure 1

Bar graphs of average performance in English and Spanish language assessments across groups of English monolinguals, and Spanish-English early and late bilinguals. Error bars represents standard error.

Figure 2

Bar graphs of average performance in the production of English words between groups of English monolinguals, and Spanish-English early and late bilinguals. Error bars represents standard error.

Figure 3A

Region of interest analyses in the bilateral superior temporal gyrus and bilateral rolandic operculum in AoA × SES ANOVA. Group comparisons in each ROI at the second level of analysis (e.g., early bilinguals vs. late bilinguals) contrast the conditions of English syllables vs. baseline. Comparisons show brain activity between groups of equivalent socioeducational background (SES). Yellow: high SES; Blue: low SES. Brain areas colored in green in panel A of the bilateral superior temporal gyrus ROI display the specific coordinates that increased in activation in the bilateral STG depending on AoA and SES. ROI p-value < 0.05, cluster size k < 20.

Figure 3B

Region of interest analyses in the bilateral middle frontal gyrus and bilateral inferior parietal lobule in AoA × SES ANOVA. Group comparisons in each ROI at the second level of analysis contrast the conditions of English syllables vs. baseline. The same color conventions as Figure 3A are employed here. ROI p-value < 0.05, cluster size k < 20.

Figure 4

Region of interest analyses in the bilateral superior temporal gyrus, the bilateral rolandic operculum, the bilateral middle frontal gyrus, and the bilateral inferior parietal lobule in AoA × L2 proficiency ANOVA. Group comparisons in each ROI at the second level of analysis contrast the conditions of English syllables vs. baseline. Comparisons show brain activity between groups of equivalent L2 proficiency level. Red: high L2 proficiency; Cyan: low L2 proficiency. Purple represents the main effect of proficiency collapsed with the contrast of high proficiency vs. low proficiency which showed increased activity in virtually the same coordinates. ROI p-value < 0.05, cluster size k < 20.