Orthographic depth and the interaction of visual and auditory processing in word recognition

We studied the influence of word frequency and orthographic depth on the interaction of orthographic and phonetic information in word perception. Native speakers of English and Serbo-Croatian were presented with simultaneous printed and spoken verbal stimuli and had to decide whether they were equivalent. Decision reaction time was measured in three experimental conditions: Clear print and clear speech, degraded print and clear speech, and clear print and degraded speech. Within each language, the effects of visual and auditory degradation were measured, relative to the undegraded presentation. Both effects of degradation were much stronger in English than in Serbo-Croatian. Moreover, they were the same for high- and low-frequency words in both languages. These results can be accounted for by a parallel interactive processing model that assumes lateral connections between the orthographic and phonological systems at all of their levels. The structure of these lateral connections is independent of word frequency and is determined by the relationship between spelling and phonology in the language: simple isomorphic connections between graphemes and phonemes in Serbo-Croatian, but more complex, many-to-one, connections in English.