text: Abstract:
  
  Learning language is a cornerstone in the cognitive development during the first year of life. A fundamental difference between infants growing up in monolingual versus bilingual environments is the necessity of the latter to discriminate between two language systems since very early in life. To be able to learn two different languages, bilingual infants will have to perceive the regularities of each of their two languages while keeping them separated. In this thesis we explore the differences between monolingual and bilingual infants in their early language discrimination abilities as well as the strategies that arise for each group as a consequence of their adaptation to their different linguistic environments.
  In chapter two, we examine the capacities of monolingual and bilingual 4-month-old infants to discriminate between their native/dominant language from foreign ones in the auditory domain. Our results show that, in this context, bilingual and monolingual infants present different brain signals, both in the temporal and the frequency domain, when listening to their native language. The results pinpoint that discriminating the native language represents a higher cognitive cost for bilingual than for monolingual infants when only auditory information is available.
  In chapter three we explore the abilities of monolingual and bilingual 8-month-old infants to discriminate between languages in the visual domain. Here we show to infants never exposed to sign languages videos of two different sign languages and we measure their discriminatory abilities using a habituation paradigm. The results show that at this age only bilingual infants can discriminate between the two sign languages. The results of a second control study points in the direction that bilinguals exploit the information coming from the face of the signer to make the distinction.
  Altogether, the studies presented in this thesis investigate a fundamental ability to learn language - specially in the case of bilingual environments - which is discriminating between different languages. Compared to a monolingual environment, being exposed to a bilingual environment is characterized by receiving more information (2 languages) but with less exposure to each of the languages (on average half of the time to each of them). We argue that the developmental brain is as prepared to learn one language from birth, as it is to learn two. However, to do so, monolingual and bilingual infants will develop particular strategies that will allow them to select the relevant information from the auditory and visual domains.