Adult subjects refer to individuals who are over the age of 18 and are typically included in research studies that focus on various aspects of adult development, behavior, health, and cognition. Researchers may study adult subjects to better understand factors that influence their psychological well-being, decision-making processes, social relationships, and overall quality of life. Studies on adult subjects can also explore the effects of aging, lifestyle choices, and environmental factors on health outcomes and behavior. Overall, research on adult subjects plays a critical role in advancing our understanding of human development and promoting evidence-based interventions to support adult well-being.