Learning a second language is usually difficult and often when we speak it we cannot disguise our origin or accent. However, there are important differences between individuals with regard to the degree to which a second language is mastered, even for people who have lived in a bilingual environment since childhood.

Members of the Cognitive Neuroscience Research Group (GRNC) linked to the Barcelona Science Park have studied these differences. By comparing people who are able to perceive a second language as if they were native speakers of that language with people who find it very difficult to do so, they have observed that the former group is also better at distinguishing the sounds of their own native language. However, there is no difference between the two groups when they hear sounds that do not form part of the language.

The results of this research, “are very promising for predicting an individual’s aptitude for learning languages and could be useful for designing strategic protocols and programs that optimize successful learning outcomes», explains Begoña Díaz of the GRNC, one of the authors of the study, together with Albert Costa and Núria Sebastián from the Department of Basic Psychology in the Faculty of Psychology of the University of Barcelona (UB), who also form part of the GRNC.

In order to study individual differences in the perception of speech, the authors of the research evaluated the perceptive abilities of 126 university students born in the Barcelona area, who came from families that only speak Spanish and who therefore learned Catalan when they started compulsory schooling. Thus all of them were born and brought up, and lived in a bilingual environment. This population is ideal for the study as Catalan has some vowel sounds that most native Spanish speakers find particularly difficult to perceive. 

From the initial cohort, 31 people were selected who corresponded to two different groups: the most and the least successful when it came to perceiving the sounds of the second language (Catalan). The ability of the brain to register differences when faced with audio stimuli was measured for these 31 individuals. To do this, the electrophysiological response of their brains to different sounds was recorded and the amplitude of an electrical wave called the mismatch potential was calculated. Since the amplitude of this wave increases with the increasing ability of the brain to register an auditory change, comparing the amplitude of the mismatch potential between the different groups allows us to establish whether there are differences in auditory processing. 

In order to assess the subjects’ general auditory capacity (non-linguistic) all 31 of the selected participants listened to tones composed of different frequencies, of different lengths and which were ordered differently. Linguistic auditory capacity was measured by exposure to vowel sounds in the mother tongue (Spanish) and to vowel sounds in a language that was unknown to the participants (Finnish).

The results showed similar amplitudes of the mismatch potential for the two groups when the participants listened to sounds that were not from their language. In contrast, when they heard sounds from their own language (Spanish) the amplitude of the wave was significantly larger for those individuals who perceive the second language (Catalan) better.

“Therefore, these results show that there is a positive correlation between specific speech discrimination abilities and the ability to learn a second language, which means that the individual ability to distinguish the specific phonemes of the language, both in the case of the mother tongue and in the case of other languages, is, without a doubt, a decisive factor in the learning process, and the ability to speak and master other languages,” concludes Begoña Díaz. 

Article: “Brain potentials to native phoneme discrimination reveal the origin of individual differences in learning the sound of a second language”, Begoña Díaz, Cristina Baus, Carles Escera, Albert Costa and Núria Sebastian-Gallés. Proceedings of the National Academy of Sciences (PNAS), DOI: 10.1073/pnas.0805022105