1 Introduction

At present, approximately two thirds of the world’s population is bilingual. Globalisation, migration and decreasing gaps between different cultures and countries make the ability to speak two or more languages necessary, and, consequently, the number of bilingual people increases steadily. The ever-increasing, significant number of people speaking two or more languages has caused high interest, among psychologists, educators and also psycholinguists, in the cognitive and cerebral study of the bilingual. An important part of the research is the study of bilingual aphasia, meaning the loss of the capability to comprehend and/or speak a language, either totally or in part, which is a result of brain injuries often caused by diseases, such as strokes or tumours, war injuries or car accidents (cf. Myers-Scotton 2006: 317). Studying bilingual aphasia and its impacts on the bilingual’s different languages contributes to finding an answer to the question of how two or more languages are organised and represented in the brain. In so doing, this field of research posits hypotheses concerning the cerebral organisation of language in general and the parts of the brain which function for its production. After having defined the terms bilingualism and bilingual, which is a necessary prerequisite to avoid confusing ambiguities in the following text, this essay will illustrate the most common patterns of language recovery and their relative incidence. This illustration will be followed by an overview of early suggested and attempted explanations for the questions about which brain mechanisms are responsible for the various patterns, why a certain patient shows a certain recovery pattern and why one language in some cases remains more intact than the other, or why sometimes one is preserved, while the other is lost entirely. Finally, the essay will outline the findings of recent research and their contribution to the cognitive study of language.

2 Who is a Bilingual?

To begin with, it is necessary to define the term bilingualism in order to give a comprehensible description of bilingual aphasia and its components. The opinions on the question of what constitutes a bilingual are deeply divided among authors and researchers dealing with this topic. Most definitions are imprecise and, thus, leave room for interpretations and speculations. Steinberg and Sciarini, for example, say that “a person is bilingual if he or she knows: (1) two languages in the same modality, for example, two speech-based languages [...], or (2) two languages based on different modalities, e.g. spoken German and American Sign Language [...].” (Steinberg & Sciarini 2006: 160-161). This

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definition includes the fact that bilingualism does not only refer to spoken languages, but that it is also an appropriate term for a person’s knowledge of non-verbal languages, such as sign language, or indeed written languages. Nevertheless, it does not make clear what “to know” these languages means and to what degree the person has to make use of them to be called a bilingual. Dictionaries usually give an even more vague description and refer to bilingualism simply as “the ability to speak two languages” (www.m-w.com/dictionary/bilingualism) and obviously take into account neither the speaker’s proficiency in the different languages nor the frequency of their use. These two examples alone show the relative nature of bilingualism, which is also pointed out by Paradis, who announces that there is no such thing as a universal definition, since they differ depending on the criteria they are based on. The main emphasis can be placed on the degree of proficiency, the languages’ relation concerning their frequency of use, the context of acquisition and use, structural differences between the languages, fluency, lexical accuracy etc., and it is therefore of paramount importance to collect as much data as possible about the patients’ bilingual backgrounds in case-studies on aphasia (cf. Paradis 2004: 2-3). However, for this essay the broad definition given by Myers-Scotton is sufficient and appropriate and can therefore serve as a basis for the following discussion of bilingual aphasia. She defines bilingualism as “the ability to use two or more languages sufficiently to carry on a limited casual conversation” (Myers-Scotton 2006: 44).

3 Language Recovery Patterns in Bilingual Aphasics

The study of language recovery patterns is a very important part in the field of bilingual aphasia, since it can give a useful insight into the organisation and representation of language in the brain and, consequently, it can contribute significantly to the development and improvement of rehabilitation programs for patients suffering from aphasia (Kroll & de Groot 2005: 516). In the following paragraphs, the most common patterns of recovery and, after that, their relative incidence will be presented.

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3.1 The Basic Recovery Patterns

There are six basic patterns of recovery classified by Paradis in 1977, namely parallel, differential, successive, antagonistic and selective recovery. One speaks of parallel recovery if the patient’s languages are impaired in the same ways and then regained at the same rate. The post-onset speech parallels the premorbid proficiency in the different languages, which is the reason for its denotation (cf. Paradis 2004: 63). Differential recovery, on the other hand, is the description of those cases in which the languages are impaired to a different extent, meaning that at least one language is impaired more strongly than the others. Nevertheless, the patient’s abilities do increase steadily in all his languages. These two patterns are also described as synergistic recovery, since the restoration of one language is simultaneous with the restoration of the other (cf. www.fask.uni-mainz.de/user/horschmann/Aphasie+Biling.html).

A third pattern is successive recovery. As the name already implies, the term refers to the sequential recovery of the languages, that is to say the languages are restored one after the other (cf. Myers-Scotton 2006: 318).

Paradis speaks of antagonistic recovery if the different languages are not available at the same time, which means that the ability to speak the language which is first available to the patient decreases to the same degree as the ability to speak a second language increases. Finally, the language first recovered by the patient disappears (cf. Paradis 2004: 63). The term selective recovery is used for cases of patients who do not regain any recovery of at least one of the languages they spoke premorbidly, while blended recovery refers to those who mix their languages in situations where this is inapplicable, but yet do it systematically. There are patients reported who blend their languages on nearly all linguistic levels (cf. Myers-Scotton 2006: 319).

Of course, these patterns do not cover all cases of bilingual aphasia, and there are numerous exceptions from the previously presented recovery patterns. They can only give an overview of the most common occurrences. Paradis himself emphasises that