Non-native speech perception in adverse conditions: A review <s> Types of listener <s> Because the field of bilingualism is still relatively new, studies in the linguistics, psycholinguistics, language development and neurolinguistics of bilingualism have often produced conflicting results. It will be argued in this paper that some of the difficulties encountered by researchers could have been lessened, if not avoided, had close attention been paid to methodological and conceptual issues. Among the issues covered are bilingual participants, language mode, stimuli, tasks as well as models of bilingual representation and processing. Each issue is dealt with in the following way: first it is explained, then the problems it causes are discussed, and, finally, tentative solutions are proposed. Examples are taken from descriptive and experimental studies of normal bilingual adults and children as well as bilinguals suffering from aphasia and dementia. <s> BIB001 </s> Non-native speech perception in adverse conditions: A review <s> Types of listener <s> Whether in family life, social interactions, or business negotiations, half the people in the world speak more than one language every day. Yet many myths persist about bilingualism and bilinguals. Does being bilingual mean you are equally fluent in two languages, or that you belong to two cultures, or even that you have multiple personalities? Can you become bilingual only as a child? Why do bilinguals switch from one language to another in mid-sentence? Will raising bilingual children confuse and delay their learning of any language? In a lively and often entertaining book, an international authority on bilingualism, son of an English mother and a French father, explores the many facets of bilingualism. In this book, Francois Grosjean draws on research, interviews, autobiographies, and the engaging examples of bilingual authors. He describes the various strategies - some useful, some not - used by parents raising bilingual children, explains how children easily pick up and forget languages, and considers how bilingualism affects the experience and expression of emotions, thoughts, and dreams. This book shows that speaking two or more languages is not a sign of intelligence, evasiveness, cultural alienation, or political disloyalty. For millions of people, it's simply a way of navigating the complexities of life. <s> BIB002
In most research related to non-monolingual speakers there is considerable uncertainty over the terms which define the linguistic profile of such populations. A frequent division in the literature is that between native versus nonnative speakers/listeners. In the case of speakers who are monolingual until adulthood or at least until adolescence, there is little doubt as to which of their languages is their native or first one. In these cases, languages learned after adolescence can be classified as second languages (L2s) or foreign languages (FLs). These terms are frequently used interchangeably but, at least for perceptual studies, it is necessary to make a distinction. In broad terms, whether a language is considered to be 'second' or 'foreign' can be defined as a function of geographical setting and amount of presence in the community. The term L2 applies to languages learned after the L1 is fully established, and which are in widespread use in the community where the speaker is located at the time of acquisition, as is the case for many immigrants. In contrast, a FL is not widely present in the speaker's environment, even if contact with it through the media or other sources is frequent. A FL is typically learned through instruction and lacks the massive, natural and native input which characterises L2 acquisition. This difference in input is what makes the distinction particularly relevant for phonetic studies. When dealing with L2 speakers we can assume that their behaviour is not provoked by defective input, whereas in the case of FL speakers, not only the quantity but even more so the quality of input maybe suspect and a dominant factor in speech perception. It is usually assumed that speakers possess native competence in their L1. However, this is not always so. There are cases in which, through attrition (e.g., immigrants who lose contact with their L1) or interrupted exposure before full acquisition (e.g., children who stop receiving L1 input before the language has been completely established), individuals may not have so-called 'native' competence in their L1 or native language. Another issue which is relevant to phonetic and perceptual studies is homogeneity of competence in the native population. In any one group of native listeners there may be relevant differences with respect to their hearing acuity, to their familiarity (perceptual competence and experience) with different varieties of the language, including non-native varieties, and with respect to their phonetic awareness, all of which can contribute variability in test results. The question of variable competence reaches an extreme in bilingualism. There are frequent cases in the literature in which L2 and even FL speakers are denoted 'bilingual'. While correct in the literal sense of possessing two languages, a close definition is required to properly assess the competence of listener populations used in perception studies. A strict definition of a bilingual supposes equal and native competence in the two languages  which, it may be argued, is rather a rare situation. The term 'bilingual' is sometimes used for those situations in which the two languages are acquired at the same time, though a more precise denomination for this situation is 'simultaneous bilingualism'. In practice, most bilinguals have a dominant language for particular domains of life, which may vary at different stages of their life. This is different from the most active language at different points of their daily life depending on the topic, context and interlocutors. In fact it has been suggested that bilinguals move along a continuum of language activation, at one end of which only one of their languages is active and at the other end their activation is totally bilingual because they are operating simultaneously in the two languages  . Just as language activation maybe seen as a continuum, bilingualism itself may be a scale ranging from true monolinguals to strict bilinguals   . In between lie speakers with different degrees of competence in each of the two (or more) languages (however, see BIB002 . Despite the complexity of the issue, when comparing across experimental studies it is useful to distinguish L2 speakers, FL speakers and those who have native-like or near-native competence in two or more languages. However, as we shall see, these distinctions are not observed frequently in the literature and the true nature of listener populations can be difficult to gauge from the written record. Likewise, without strict criteria of bilingualism, division points amongst speaker groups according to age of arrival (AOA) are somewhat arbitrary and variable. Again this makes comparisons amongst differing groups problematic, and means that careful comparisons between reported studies are needed to ascertain the linguistic profile of the analysed groups. Differences in results should not be attributable to methodological differences in subject selection, after the fact, as is often the case (see BIB001 . Given the many different criteria used in NN studies to select populations and the inter-and intra-study heterogeneity of listener populations, it is difficult to draw sound generalizations and comparisons about non-monolingual listener perception. In what follows we will use the term "bilingual" to refer to speakers with near-native competence in two languages, typically from childhood. For the later acquisition of another language we will use L2/FL jointly or separately as the need arises.