Mapping common ground: relationships between sensory-processing sensitivity, introversion-extraversion, openness to experience and intelligence

© 2018 Dr. Jodie ValpiedSensory-processing sensitivity encompasses the overlapping characteristics of low sensory threshold, heightened awareness of and reactivity to sensory stimuli, heightened top-down inhibitory processes, and deep processing of sensory information. Both introversion and openness to experience (also encompassing the narrower facet of intellect) have been separately linked to markers of sensory-processing sensitivity, even though introversion and openness/intellect are usually negatively correlated with each other. Introversion and openness/intellect have rarely been included simultaneously in analyses of relationships with sensory-processing sensitivity. Including these two personality factors simultaneously in analyses is important, given the negative bivariate relationship between introversion and openness/intellect can obscure positive relationships with other variables, through statistical suppression effects. The Highly Sensitive Person Scale is a self-report measure of sensory-processing sensitivity of potential utility for further researching relationships between sensory-processing sensitivity, introversion and openness/intellect. However, there is lack of clarity regarding the factor structure of the Highly Sensitive Person Scale, with different studies reporting different factor solutions. There are several methodological issues that may have contributed to these discrepancies, and concerns that neuroticism or negative affect could contribute to spurious factors emerging for this scale. However, no known prior studies have addressed these potential issues. A series of studies were undertaken as part of this thesis, investigating the factor structure of the Highly Sensitive Person Scale, and relationships between these factors and introversion, openness/intellect, and intellectual giftedness. The final study in this thesis then sought to test whether introversion, openness/intellect or cognitive reasoning ability were related to non-invasive, physiological markers of sympathetic and parasympathetic responsivity: low frequency and high frequency heart rate variability. Studies undertaken for this thesis employed robust structural equation modelling techniques with data from a range of new or existing adult samples recruited through the community and online. All analyses controlled for neuroticism or subjective wellbeing, and for other variables where relevant, and included introversion and openness/intellect simultaneously in analyses. Results of these analyses showed that the Highly Sensitive Person Scale is best represented by three factors, Low Sensory Threshold, Situational Sensitivity and Aesthetic Sensitivity. This factor structure was unaffected by neuroticism or emotional wellbeing, and was replicated across three samples. Low Sensory Threshold was consistently, positively related to both introversion and openness/intellect. This relationship was mediated by Situational Sensitivity for introversion and by Aesthetic Sensitivity for openness/intellect. Both introversion and openness/intellect were also positively related to intellectual giftedness, when including both of these personality variables simultaneously in the model. However, contrary to expectations, there were no significant relationships between Highly Sensitive Person Scale factors and intellectual giftedness. Both introversion and openness/intellect were positively related to low frequency heart rate variability during some conditions, and openness/intellect was positively related to high frequency heart rate variability under most conditions. Cognitive reasoning had a positive relationship with low frequency heart rate variability for males, and a negative relationship with high frequency heart rate variability for females. The above findings suggest that heightened sensory-processing sensitivity may be accompanied by feeling potentially overactivated by external stimuli or by a desire to engage with aesthetic or cognitively interesting stimuli. The former is associated with introversion and the latter with openness/intellect. Some highly sensitive individuals may experience both Situational Sensitivity and Aesthetic Sensitivity aspects of sensory-processing sensitivity, given the pattern of relationships found. Common ground shared between introversion, openness/intellect and correlates such as intelligence may have important implications for further understanding these personality variables, especially given the current interest by personality theorists in mechanisms shared by extraversion and openness/intellect. The model of relationships found in this thesis could provide a useful framework for future research, and for practitioners who work in areas relevant to sensory-processing sensitivity