Behavioral and neurophysiological investigations on the bimodal processing of orthography and phonology in spoken word recognition – the effect of orthographic depth

The acquisition of orthographic representations leads to a restructuring of the organization of language in the brain. Orthographic word forms need to be connected to existing phonological word forms and the corresponding semantic representations. This restructuring of the mental lexicon leads to interdependent orthographic and phonological representations. As a consequence, extensive studies show that phonological information is automatically activated in reading in alphabetic writing systems. In the same way, a more recent line of research found evidence for a similarly automatic activation of orthographic information in spoken word recognition. Hence, language processing is bimodal in nature irrespective of the modality of the linguistic input. However, the existing literature on the bimodal processing of spoken words is limited to English and French, two languages that are considered orthographically deep. Orthographic depth is regarded as the most relevant concept for the explanation of cross- linguistic differences in all orthographically related processing. Therefore, the current thesis investigates if the orthographic depth of a writing system also influences the bimodal processing of spoken words. Two studies with several experiments are described in which late German- English bilinguals were investigated in their native and their second language. The findings of both studies provide consistent evidence for a substantial influence of orthographic depth on bimodal word processing. Both the nature and the extent of this influence systematically varied as a function of the orthographic depth of the target language. Orthographic information led to facilitated processing in English, but inhibited processing in German. Orthographic information showed earlier, longer lasting, and more stable influences on spoken word recognition in English, while phonological influences were prevalent in German. These findings, thus, indicate that the bimodal processing of spoken words is modulated by the orthographic depth of the writing system. They also show that late bilinguals flexibly adapt processing mechanisms to the target language. The results are in line with models of bilingual word recognition such as the Bimodal Interactive Activation Model (BIAM).