Natural Dopamine: Nature’s Seven DIURNAL Environmental Enrichment Properties in Changing Visual Complexity

Background/Objectives: Time spent in unchanging environments is associated with poorer brain, cognitive and mental health outcomes, while environmental enrichment for humans is measured by how much nature is present rather than how it changes. Methods: This study quantified nature’s changing visual complexity using a large-language-model scoring method validated against a deep-learning complexity metric previously tested using event-related potentials. Photos were taken of a natural scene, a tree, and the sky across minutes, days, and seasons (1115 photographs; 2024 to 2026). Results: The analysis identified seven quantitative properties describing nature’s dynamic environmental enrichment in changing visual complexity: Dichotomy, Inclination, Unpredictability, Renewal, Net balance, Amplitude, and Level (DIURNAL). A quantitative simulation then showed that a natural view offers more change than indoor and urban views, consistent with the argument that unchanging environments are detrimental to the brain, which is hypothesised here to act through a dopaminergic pathway. Conclusions: DIURNAL raises questions for biophilic design and for how neurotypical and neurodivergent brains respond to change in visual complexity in nature, digital environments and built environments.