Emotion has fascinated theorists for over a century, producing three major competing accounts of how bodily responses relate to emotional experience. The James-Lange theory proposed that we experience emotion as a result of our body's physiological response—rather than crying because we are sad, we feel sad because we cry. The Cannon-Bard theory countered this by arguing that physiological arousal and emotional experience occur simultaneously rather than sequentially, with the thalamus sending signals to both the body and the cortex at the same time. The Schachter-Singer two-factor theory proposed a middle path: emotion arises from physiological arousal combined with cognitive labeling of that arousal, meaning the same bodily state (such as a racing heart) might be interpreted as fear, excitement, or anger depending on context. These theories continue to inform research on how bodily states and mental interpretations combine to produce emotional experience.
Stress, a closely related phenomenon, was systematically described by Hans Selye through the general adaptation syndrome (GAS), which identifies three stages in the body's response to prolonged stress: alarm (the initial fight-or-flight activation), resistance (the body's adaptation to ongoing stressors), and exhaustion (depletion of resources, leaving the organism vulnerable to illness). It is useful to distinguish between eustress, positive and motivating stress that enhances performance (such as the anticipation before a competition), and distress, negative and harmful stress that impairs functioning (such as chronic work overload). Richard Lazarus and Susan Folkman's transactional model of stress emphasizes that stress arises not from the situation alone but from how a person appraises it; primary appraisal evaluates whether something is a threat, while secondary appraisal evaluates the resources available to cope.
People respond to stress with two broad categories of coping strategies. Problem-focused coping directly addresses the stressor by making plans, gathering information, or taking action, while emotion-focused coping manages the emotional response through techniques such as meditation or seeking social support. Both strategies have their place depending on whether the stressor is changeable. Resilience—the capacity to adapt well in the face of adversity, trauma, or significant stress—is closely linked to effective coping and may even produce post-traumatic growth. Emotional regulation research by James Gross has compared specific strategies in detail: cognitive reappraisal, which reinterprets the meaning of an emotion-triggering situation to alter its emotional impact, tends to be more effective than expressive suppression, which inhibits only the outward expression of emotion and can increase physiological stress. Finally, Julian Rotter's concept of locus of control captures an important individual difference: people with an internal locus of control believe outcomes are determined by their own actions, while those with an external locus attribute outcomes to luck, fate, or powerful others—an internal locus is generally associated with better coping and psychological well-being.