Impact of the linguistic environment on speech perception : comparing bilingual and monolingual populations

The present dissertation set out to investigate how the linguistic environment affects speech perception. Three sets of studies have explored effects of bilingualism on word recognition in adults and infants and the impact of first language linguistic knowledge on rule learning in adults. In the present work, we have found evidence in three auditory priming studies that bilingual adults, in contrast to monolinguals have developed mechanisms to effectively overcome interference from irrelevant information in the speech signal. Preliminary results on toddlers indicate no differences in the recognition of mispronounced words between bilinguals and monolinguals. Additionally, knowledge about rules in the first language was shown to have an impact on general rule learning abilities, while we did not detect an influence of bilingualism in this process. In summary, we have found evidence for an impact of the linguistic environment on the processing of indexical variability in word recognition as well as on rule learning. Bilinguals seem to have adapted to increased variability in their daily speech environment. In addition, rule extraction from unknown language input was unaffected by those adaptations but influenced by linguistic knowledge.El principal objetivo de este trabajo fue investigar cómo el entorno lingüístico afecta la percepción del habla. Con esta finalidad se exploraron los efectos del bilingüismo en el reconocimiento de palabras y el efecto de la lengua materna en el aprendizaje de reglas. Para ver los efectos del bilingüismo en el reconocimiento de palabras se realizaron tres estudios en adultos explorando el efecto de facilitación por repetición, que mostraron que las personas bilingües han desarrollado mecanismos que les permiten minimizar las interferencias que ejerce la información irrelevante en la señal del habla. Por otro lado, se realizó un estudio con niños pequeños cutos resultados sugieren que no hay diferencias en el reconocimiento de palabras mal pronunciadas entre niños pequeños bilingües y monolingües. Respecto al efecto del conocimiento lingüístico de la lengua materna en el aprendizaje de reglas, se mostró que tiene un impacto en las habilidades generales para el aprendizaje de reglas aunque no se ha detectó una influencia del bilingüismo en dicho proceso. En resumen, se ha mostrado que el bilingüismo minimiza los efectos negativos de la variabilidad en el reconocimiento de palabras. Los bilingües parecen haberse adaptado a una mayor variabilidad en su entorno de habla cotidiana. Por el otro lado, se ha visto que la capacidad para extraer reglas de una lengua desconocida no está afectada por estas adaptaciones si no que está influenciada por los conocimientos lingüísticos en la lengua materna

An Effect of bilingualism on the auditory cortex

Two studies (Golestani et al., 2007; Wong et al., 2008) have reported a positive correlation between the ability to perceive foreign speech sounds and the volume of Heschl's gyrus (HG), the structure that houses the auditory cortex. More precisely, participants with larger left Heschl's gyri learned consonantal or tonal contrasts faster than those with smaller HG. These studies leave open the question of the impact of experience on HG volumes. In the current research, we investigated the effect of early language exposure on Heschl's gyrus by comparing Spanish–Catalan bilinguals who have been exposed to two languages since childhood, to a group of Spanish monolinguals matched in education, socio-economic status, and musical experience. Manual volumetric measurements of HG revealed that bilinguals have, on average, larger Heschl's gyri than monolinguals. This was corroborated, for the left Heschl's gyrus, by a voxel-based morphometry analysis showing larger gray matter volumes in bilinguals than in monolinguals. Since the bilinguals in this study were not a self-selected group, this observation provides a clear demonstration that learning a second language is a causal factor in the increased size of the auditory cortex.This work was supported by grants from the Spanish Ministerio de Ciencia e Innovación (JCI-2009-04492, PSI2010-20168; SEJ2009-09072, Consolider-Ingenio2010-CDS-2007-00012), the Catalan Government (SGR 2009-1521), and the French National Agency for Research (ANR 2010 BLAN 1403 01). N.S.-G. received the prize ICREA Acadèmia for excellence in research, funded by the Generalitat de Catalunya. We thank Kimberly Brink for the English correction of the manuscript

An Effect of bilingualism on the auditory cortex

Two studies (Golestani et al., 2007; Wong et al., 2008) have reported a positive correlation between the ability to perceive foreign speech sounds and the volume of Heschl's gyrus (HG), the structure that houses the auditory cortex. More precisely, participants with larger left Heschl's gyri learned consonantal or tonal contrasts faster than those with smaller HG. These studies leave open the question of the impact of experience on HG volumes. In the current research, we investigated the effect of early language exposure on Heschl's gyrus by comparing Spanish–Catalan bilinguals who have been exposed to two languages since childhood, to a group of Spanish monolinguals matched in education, socio-economic status, and musical experience. Manual volumetric measurements of HG revealed that bilinguals have, on average, larger Heschl's gyri than monolinguals. This was corroborated, for the left Heschl's gyrus, by a voxel-based morphometry analysis showing larger gray matter volumes in bilinguals than in monolinguals. Since the bilinguals in this study were not a self-selected group, this observation provides a clear demonstration that learning a second language is a causal factor in the increased size of the auditory cortex.This work was supported by grants from the Spanish Ministerio de Ciencia e Innovación (JCI-2009-04492, PSI2010-20168; SEJ2009-09072, Consolider-Ingenio2010-CDS-2007-00012), the Catalan Government (SGR 2009-1521), and the French National Agency for Research (ANR 2010 BLAN 1403 01). N.S.-G. received the prize ICREA Acadèmia for excellence in research, funded by the Generalitat de Catalunya. We thank Kimberly Brink for the English correction of the manuscript