The Cost of a Narrow Lens: Why Morphological Processing and Learning Research Needs More Languages

The majority of words across the world’s languages are composed of smaller meaningful units called morphemes (e.g., mis-trust-ful-ness). Research over the past 50 years has shown that such words are processed through morphological analysis—the decomposition of complex words into their meaningful subparts. While psycholinguistics has made significant progress in understanding this process during reading, most evidence comes from a narrow range of languages and morphological types. In this paper, we quantify linguistic and typological diversity in morphological processing and acquisition research from 1975 to 2025. Articles were coded for language(s), morphological type(s), participant type, and publication year. Our survey revealed that about 40% of the studies come from English and about 74% come from Indo-European languages (e.g., French, Spanish, German). We also found that about 53% of the studies focused on suffixation, the most frequent morphological process in English. We argue that this narrow scope limits theoretical progress. Many languages form complex words through reduplication, infixation, circumfixation or nonlinear morphology that differ structurally from English suffixation, and that pose learning and processing challenges that would not arise in English. We conclude that expanding linguistic diversity is necessary for building a more comprehensive account of morphological learning and processing.