JAMES-LANGE. "[The] evaluation of a stimulus causes a physical reaction that is experienced as a specific emotion", is the brief explanation we can find in the APA handbook (Dess, 2010, p. 6-7) in relation to this theory. In other words, we first react physically to the stimulus, and then we feel the emotion. As Robert Zajonc points out, emotion is prior to thought according to this theory, which received the name of its two first ideologues, William James, whose text What is an emotion? (1884) is the basis of this theory; and Carl Lange, who arrived at similar conclusions at the end of the 19th century (Dalgleish, 2004, p. 582). Apart from being a physiological response, an emotion includes a psychological reaction. James, as Darwin also suggested, believed in the strength of facial expressions, which would later constitute the theory of "facial feedback" (The Science of emotions, 2019, p. 12).
CANNON-BARD. “Physical changes and emotional experience occur at the same time” (Dess, 2010, p. 6-7). It seems to be scientific evidence that physical changes and emotional experience are simultaneous since information is provided to both the amygdala and the brain cortex at once after the stimulus happens (The Science of emotions, 2019, p. 12). This early neuroanatomical theory -it was partially studied in cats with brain lesions- delivered by Walter Cannon and Philip Bard in the 1930s showed the importance of the hypothalamus (Dalgleish, 2004, p. 583). These experiments with brain lesions were the basis of the future 'neuromusical' research.
SCHACHTER-SINGER, The two-factor theory. Certain arousals and behaviors belong to several emotions, and they often lack information to know which emotion they account for. An evaluation of the situation and the physiological response lets one know which emotion is felt (Dess, 2010, p. 6-7). For Stanley Schachter and Jerome E. Singer, this rational element seemed to be key to make us feel a specific emotion, still not such much as in the Cognitive Appraisal Theory, which defends that the thought should occur before the response (The Science of emotions, 2019, p. 12).