Personality Neuroscience and Psychological Well-Being in Nigeria: A Cross-Cultural Validation and Neurobiological Extension of the Big Five Model

The Big Five personality model has demonstrated cross-cultural validity across numerous societies, yet its neurobiological underpinnings and their relationship to psychological well-being have not been examined in a Nigerian population, where both sociocultural personality expression and neurobiological stress exposure patterns differ substantially from Western reference samples. This study extends the Big Five model into a Personality Neuroscience and Well-Being framework through a cross-sectional multi-method study of 400 adults in Lagos State and Kano State, stratified equally by zone, gender, and educational level. Phase 1 administers the NEO Personality Inventory-3, Ryff's Scales of Psychological Well-Being, the Big Five Inventory-2, and the Emotion Regulation Questionnaire. Phase 2 collects salivary cortisol (morning and evening samples) and hair cortisol as neurobiological stress markers in 200 participants. Structural equation modelling in AMOS tests the personality-neurobiology-well-being model. Confirmatory factor analysis evaluates Big Five structural validity in the Nigerian samples. Available personality psychology literature from Nigeria identifies neuroticism and conscientiousness as the most cross-culturally stable Big Five predictors of well-being, with cortisol reactivity as a hypothesised neurobiological mediator. DeYoung's Cybernetic Big Five Theory and Gray's Reinforcement Sensitivity Theory provide the neurobiological theoretical framework. The original contribution is a Nigerian Personality Neuroscience Model extending cross-cultural personality theory with biological data from sub-Saharan Africa. Keywords: Big Five personality, personality neuroscience, psychological well-being, cortisol, Nigeria.