The four major theories of emotion propose distinct causal sequences for how an emotional response is generated when encountering a stimulus, such as a snake. According to the James-Lange theory, arousal leads directly to a physiological response like heart pounding and sweating, which then produces the emotion of fear. The Cannon-Bard theory asserts that arousal simultaneously triggers both the physiological response and the emotion. The Schachter-Singer two-factor theory posits that arousal causes a physiological response that must be combined with a cognitive label, such as thinking 'I’m scared', to produce the emotion. Finally, Lazarus' cognitive-mediational theory suggests that arousal is first followed by an appraisal, which then simultaneously elicits the emotion and physiological response.