Exploring the psychology and genetics of sensory processing sensitivity in multicultural South Africa

Abstract

Sensory Processing Sensitivity (SPS) is a personality trait charaterised by deep cognitive processing, heightened awareness of sensory stimulation, strong emotional reactivity and a propensity to feel overwhelmed. Individuals with high levels of SPS are referred to as Highly Sensitive Persons (HSPs) and are thought to comprise 20-35% of the population. A defining feature of HSPs is their permeability to environmental influence, rendering them susceptible to disproportionately negative behavioural outcomes in adverse contexts, but disproportionately positive outcomes in nurturant contexts, when compared to non-HSPs. Since its conceptualisation in the late 1990s, the SPS construct has gained significant traction in the scientific literature and has been recently merged into a cross-disciplinary metaframework known as Environmental Sensitivity (ES). Furthermore, because of the simplicity and accessibility of its attendant instrument(the Highly Sensitive Person Scale [HSPS]), and its intuitive explanation of human behavioural differences, SPS theory has garnered notable popularity in the public media. However, SPS was conceptualised, and has been further developed, using culturally homogeneous and mostly Caucasian-centric samples. To date, the trait has not been explored anywhere on the ethnically and culturally diverse African continent. To address this gap in the literature, this doctoral research aimed to provide an initial psychological and biological exploration of SPS, and the HSPS, in diverse South African samples. Four studies were conducted, namely: 1. a pilot investigation of the HSPS amongst university-level psychology students, 2. factor and latent class analysis of the HSPS, 3. an investigation into the association between SPS, the five-factor model of personality, and adjustment to the first year of university in a multi-ethnic student sample, and 4. a broad examination of the influence of SPS, and other physiological (birth weight, temperament) and genetic (5-HTTLPR andDRD4) markers of the larger ES framework, on childhood internalising and externalising behaviour amongst Black African members of the Birth to Twenty Plus cohort. Across all studies, the HSPS demonstrated acceptable internal consistency reliability. The psychometric properties of the instrument aligned with previous reports, except for factor analysis which revealed a unique, five-factor structure. SPS correlations with the five-factor model of personality were all in predicted directions. In line with hypothesised expectations, HSPs were less well-adjusted to university (Study 3) and displayed more internalising and externalising behavioral problems (Study 4) than their non-sensitive counterparts. Environmental mediation of outcomes for HSPs was inconsistent, neither fully supporting nor fully contradicting SPS theory. There was no clear association between SPS and genetic variation in the 5-HTTLPR,or in theDRD4gene. On balance, this exploratory doctoral research found evidence to support both SPS theory, and its attendant instrument, the HSPS. However, some of the results high-lighted inconsistencies that will need to be resolved in future studies. Nevertheless, SPS appears to be a meaningful personality construct with important implications and thus deserves further research, especially in an African context