The ability to make inferences from linguistic information (spoken and written discourse) is regarded as a significant factor in successful reading success. Although, this relationship has been researched with English first language/monolingual cohorts (see Cain, Oakhill, Barnes, & Bryant, 2001; Oakhill & Cain, 2012; Silva & Cain, 2015), there is a paucity of research on inferential skills in other languages as well as in bilinguals or second language learning contexts. Therefore, the present study focused on investigating inferential skills and reading comprehension in two different languages (Thai and English) within the same group of adult students at a college in Thailand. The primary objectives of this study, as reported in this thesis, were to examine the reciprocal relationships of inferential skills within Thai and English, and to investigate whether inferential skills can predict reading comprehension both within each language and across languages (Thai-L1 and English-L2). The study involved measures of inferential skills, reading comprehension, vocabulary and listening comprehension in Thai and English, following appropriate adaptation, piloting and revision. Raven’s Advanced Progressive Matrices test (short form) was also used to explore non verbal reasoning, and a questionnaire was used to provide background details about the participants and their views on reading comprehension strategies. Data collection was conducted at one campus of a university in Thailand. All ten measures were administered to a group of 220 Thai undergraduate students. The results demonstrated a significant inter-relationship between inferential skills in Thai (L1) and English (L2). Scores on the inferential tasks were also related to reading comprehension within the same language. Furthermore, the findings from hierarchical regression analyses indicated that the addition of inferential skill scores significantly increased the predictability of reading comprehension in the same language, after controlling for within-language vocabulary levels (and listening comprehension in the case of Thai) and non-verbal reasoning. Analyses across languages showed positive correlations between Thai inferential skills and English reading comprehension, and between English inferential skills and Thai reading comprehension. Hierarchical regression analyses indicated that the addition of English inferential skills scores predicted extra variability in Thai reading comprehension, after controlling for English and Thai language related skills and non-verbal reasoning measures, but the addition of Thai inferential skills scores did not influence the level of prediction of English reading comprehension after controlling for the same variables. The reading strategies questionnaire did not reveal a significant relationship with either the Thai or the English reading comprehension scores. However, relationships between self-reported reading comprehension strategies and inferential skills scores were found, though the correlations were relatively small.
Overall, the findings are consistent with the ability to make inferences being an important component of successful text comprehension–although there is little evidence of awareness influencing performance among the current participants. The influence of inference making does not seem to be explained by more general language skills (such as vocabulary and listening comprehension), nor by more general (non-verbal) reasoning skills, and it has the potential to occur across languages (from English to Thai in the present study), although within language influences may be larger than between languages. These findings have both theoretical and practical implications, which are discussed in this thesis.