Measurement Reliability of Individual Differences in Sentence Processing and the Influence of Cognitive Capacities

Over the last few years, evidence has accumulated showing that individual differ- ences in sentence processing can potentially be explained by individual differences in the comprehender’s cognitive capacities. This has lead to the conclusion that indi- vidual differences cannot be treated simply as variance, but as something that needs to be included in psycholinguistic theories of human sentence processing. However, which aspects of domain-general cognitive capacities interact with language pro- cessing remains unclear. In this thesis, 40 native speakers of German completed a battery of 14 verbal and cognitive skill assessments, and read a total of 16 texts distributed across four sessions. First, Bayesian statistical modelling was performed to establish whether individual differences remained stable for one individual and across sessions (test-retest reliability). Then I asked which cognitive capacities were potentially the source of individual differences in sentence processing. Results show that lower-level effects such as word length and word frequency stayed stable over time and were strongly correlated with reading fluency. Higher-level effects, such as surprisal and dependency length only remained stable across the two eye-tracking sessions and individual differences in these effects were explained by differences in reading fluency, working memory and cognitive control