Emotions are feelings or affective experiences that are characterized by physiological changes and generally lead to behavioral responses. Emotions have several key characteristics - they are associated with instincts, are products of perception, involve core feelings, and bring about physiological changes in the body. Emotions differ between individuals, can be aroused by various stimuli, rise abruptly but subside slowly, and one emotion can give rise to similar emotions. Emotions are present in all living organisms and at all stages of development.