This chapter presents a comparative analysis of the use of different linguistic and non-linguistic knowledge sources (KSs) in first language (L1) and second language (L2) lexical inferencing from written texts, by the English, Persian and French speakers in our study. As an approach to exploring L1 influences on L2 lexical inferencing, we sought first to determine shared aspects of KS use in lexical inferencing by L1 speakers of these three Indo-European languages, as well whether these shared L1 patterns also held for L2 inferencing. We then identified KS use patterns that differentiated L2 inferencing in English from L1 inferencing by the Persian, French and English speakers. We also explored KS use in inferring meanings for L2 words with lexical equivalents in the respective readers' L1 versus those without equivalents. The core issue of L1 influence on readers' L2 lexical inferencing was approached through a detailed analysis of KS use by speakers of Persian and French in both their L1 and in English (L2). Within-group L1 and L2 similarities, as distinguished from the other language groups' patterns, were viewed as an indication of possible L1 transfer – whether from readers' L1 linguistic knowledge or accustomed processing patterns. Finally, an analysis of lexical inferencing by the three groups in English, i.e. English L1 readers as well as Persian and French L2 readers, identified shared patterns of KS use across all three groups that did not correspond to the previously identified more 'universal' patterns. Such patterns were interpreted as a probable English text language influence in L2 inferencing.

Of primary interest in this investigation were the nature and the importance of L1 linguistic influences on readers' use of textual cues and background knowledge in L2 lexical inferencing in English. Where relevant, language-related cultural – including instructional – influences were also identified.