The languages of aphasia research: Bias and diversity

Background: It is widely believed that the vast majority of articles on aphasia published in international journals are based on observations of English-speaking patients, with a possible more general bias towards western European languages. However, to the best of our knowledge no systematic study has tried to quantify linguistic biases in aphasia research. Aims: To examine the current (first decade of the twenty-first century) representation of different languages in aphasia literature. Methods & Procedures: We examined all articles on aphasia published between 2000 and 2009 in four leading aphasiological journals: Aphasiology, Brain and Language, Journal of Neurolinguistics, and Language and Cognitive Processes, determining the language(s) spoken by the patients. We compared the proportion of articles in a given language with the estimated number of its speakers worldwide. We further analysed the relationship between the language and the methodology, content, and number of citations as well as trends applying to individual journals and changes over time. Outcomes & Results: There was a pronounced overall bias towards articles based on observations of English-speaking patients, accounting for 62% of all papers, 85% of papers on aphasia treatment, and 100% of papers that received more than 50 citations. More generally, there was a strong bias towards western European (Germanic and Romance) languages, accounting for 89% of all papers and 96% of treatment studies. In contrast, non-Indo-European languages, as well as the Slavonic and the Indo-European languages of India were strongly under-represented. Some of the most widely spoken languages in the world, such as Arabic, Hindi, Bengali, Russian, as well as Portuguese, accounted for less than 0.5% of the aphasia literature. This imbalance has not improved over the examined time period; in fact, the percentage of papers on English seems to be increasing. Conclusions: The current aphasia literature is not representative of the world's languages, neither in terms of linguistic typology nor the number of speakers. The extreme bias towards English and other western European languages limits the worldwide applicability of clinical findings (in particular in aphasia therapy) and undermines the universality of theoretical models, which are based on observations from a small number of closely related languages. We conclude that development of a more cross-linguistic approach to aphasia should be one of the priorities in future aphasia research.