Physiological psychology, often termed behavioural neuroscience, is the scientific study of how the nervous system’s structure and function give rise to behaviour, cognition, emotion, and consciousness, integrating levels of analysis from molecules and cells to brain systems and whole-organism behaviour, and drawing methodologically and conceptually from neuroscience, psychology, and biology. Its scope includes sensory and motor processes, learning and memory, motivation and emotion, language, sleep, stress, and psychopathology, investigated through complementary methods such as electroencephalography (EEG) to measure neural dynamics (pioneered by Hans Berger, 1929), functional magnetic resonance imaging (fMRI) to map activity via hemodynamic signals (Ogawa et al., early 1990s), positron emission tomography (PET) to assess metabolism and neurotransmission (Phelps et al., 1975), lesion studies that infer function from loss (from Paul Broca, 1861; Carl Wernicke, 1874; to classic cases like Phineas Gage reported by Harlow, 1848), and single-cell recording revealing neural coding principles (Hubel & Wiesel, 1959, 1962), building on foundational insights into neural integration (Charles Sherrington, 1906), synaptic plasticity and learning (Donald Hebb, 1949), action potentials (Hodgkin & Huxley, 1952), and reward circuitry (Olds & Milner, 1954). From a Christian perspective, physiological psychology explores God’s created order by studying the embodied mind, affirming that humans are “fearfully and wonderfully made” (Psalm 139:14), called to love God with heart, soul, mind, and strength (Luke 10:27), to steward the body as God’s temple (1 Corinthians 6:19–20), and to pursue the renewal of the mind (Romans 12:2), thereby encouraging ethical humility about human limits, compassion in mental health care, and integration of empirical knowledge with moral purpose. Practically, this field advances personal wellbeing by informing evidence-based interventions for stress, sleep, learning, addiction, and mood disorders, and promotes societal health by guiding public policy, education, and healthcare systems toward prevention, treatment, and flourishing grounded in an accurate understanding of brain–behaviour relationships.