Learning to read: Effects of memory consolidation on orthographic and lexical learning
In recent years the role of offline consolidation in supporting word learning has attracted great interest and has provided valuable insight into how novel spoken and written words are learned. Relatively little attention has focused on whether offline consolidation supports the learning and generalisation of novel orthographic knowledge. Meanwhile, laboratory-based approaches have proven valuable in overcoming the methodological challenges of studying reading acquisition, i.e. learning letter-sound knowledge. This thesis combines laboratory-based orthographic learning with an overnight consolidation framework to track the effects of sleep on learning novel letters and novel written words in six experiments. Experiment 1 validated the artificial orthography paradigm by using fMRI to show the novel orthography activated similar neural regions to pseudowords written in familiar orthography. Comparing recently learned words and objects additionally highlighted the componential and holistic processes that distinguish reading from object naming. Experiments 2, 3, and 4 investigated whether overnight consolidation had contrasting effects on learning novel letters and learning novel written words. All three studies showed overnight improvements in the ability to use and generalise knowledge of letters. Experiment 3 further assessed whether consolidation supported the formation of bigram representations. While the results did not show bigram consolidation, a recognition memory task indicated participants had consolidated the novel spoken words. Experiment 4 manipulated the internal statistical structure of the novel words finding, in contrast to Experiment 3, participants had consolidated the written forms of the novel words. Experiments 5 and 6 asked whether consolidated and unconsolidated spoken words would support orthographic learning. These studies failed to observe previous findings of spoken word consolidation and did not demonstrate clear effects of lexical knowledge on orthographic learning. The findings of the thesis demonstrate the importance of letter-level learning and consolidation during reading acquisition as well as highlighting the value of laboratory-based studies for understanding the interdependent trajectories of the skills involved in reading.