Degree Name

Doctor of Philosophy


School of Psychology, Faculty of Health & Behavioural Sciences


This thesis examined putative event-related potential (ERP) indices of the phasic and tonic orienting reflex (OR) in three different paradigms. The classic single series habituation paradigm was utilised for Study 1, the ERP-style dishabituation paradigm for Studies 2, 3 and 5, and the classic two-tone oddball paradigm for Study 4. In this thesis the OR is operationalised in terms of the sequential processing approach to stimulus-response elicitation described in Preliminary Process Theory (PPT) (Barry, 2006). It was expected that the late positive complex (LPC) of the ERP would represent a CNS correlate of the phasic skin conductance response (SCR) OR-yardstick. Although some similarities were observed between measures, they were not shown to represent the same process. For three of the studies, principal components analysis (PCA) was utilised to explore the separation of LPC sub-components. Four separate components were repeatedly found to contribute maximally to the LPC. These were identified as the P3a, P3b, Novelty P3 and classic slow wave, and were differentially related to the model SCR-OR. In addition, a preliminary investigation of the tonic OR compared the pre-stimulus contingent negative variation (CNV) with pre-stimulus arousal level (measured by SCL). A weak relationship was shown between these measures, which may be accounted for by an additional process of expectancy being indexed by the CNV. This thesis showed that PPT provides a better account of the LPC and its sub-components‟ stimulus-response patterns than current theoretical explanations of their functional significance. The P1, N1, P2 and N2 components of the ERP were also examined in Study 1. None showed a relationship with the phasic OR model. The data from this thesis suggest that further exploration of ERP components, employing autonomic parameters as stimulus-response yardsticks derived from a structured theoretical context such as that provided by PPT, may be useful in clarifying the determining factors that underlie the ERP in various paradigms, potentially leading to a reinterpretation of its functional significance.