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Title:Syntax and semantics: Similarities in late positive components
Author(s):Leckey, Michelle
Director of Research:Federmeier, Kara D.
Doctoral Committee Chair(s):Federmeier, Kara D.
Doctoral Committee Member(s):Dell, Gary S.; Fabiani, Monica; Fisher, Cynthia L.; Montag, Jessica L.
Department / Program:Psychology Psychology
Discipline:Psychology Psychology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):ERP, syntax, P600, aging
Abstract:The ERP component known as the (syntactic) P600 has long been associated with syntactic processing as it has consistently been seen to have a larger amplitude to critical words in sentences that contain syntactic violations or complex structure. With the later discovery of a morphologically similar component that was sensitive to violations that were more semantic in nature (semantic P600), P600 theories moved to encompass these findings into theoretical frameworks that explained how the same component could be seen in these two different instances. This is despite the fact that there has been no empirical investigation into whether or not these two positivities are in fact reflecting the same kind of underlying processing. This thesis aims to do this investigative work, using central and lateralised ERP paradigms and investigating individual differences such as familial sinistrality and aging to assess whether or not these two components are consistently elicited under the same conditions. Experiment 1 looked at sentences containing violations known to elicit the syntactic P600 or the semantic P600. The results showed that participants differed in their responses to the syntactic P600 sentences dependent on familial sinistrality profile (whether or not the individual had left handed relatives) but did not differ in response to the semantic P600 sentences. Experiment 2 followed up on these initial differences using a lateralised version of Experiment 1, biasing processing to each hemisphere individually in order to assess lateralisation patterns. The results showed that participants of differing familial sinistrality profiles differed in terms of their hemispheric contributions to processing these sentences. While those with no history of familial sinistrality had a lateralised response to the syntactic P600 sentences, the group which did have a history of familial sinistrality showed a bilateral pattern, as did both groups in response to the semantic P600 sentences. This difference in eliciting conditions again indicates that the two types of P600 responses may not be the same. Experiment 3 examined the processing of the sentences in an older adult sample. Distributional changes in the form of a frontal shift have previously been seen for the syntactic P600 in older adults, and this same pattern was found again here. However, the same shift was not seen for the semantic P600 sentences, adding further evidence to the proposal that the semantic and syntactic variants of the P600 are not reflecting the same type of processing. Taken together, the experiments in the thesis cast doubt on the multitude of theories that assume both syntactic and semantic variants of the P600 to be the same and argue that domain is an imperfect basis on which to categorise morphologically similar components.
Issue Date:2019-06-12
Rights Information:Copyright 2019 Michelle Leckey
Date Available in IDEALS:2019-11-26
Date Deposited:2019-08

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