many different physiological measures (such as heart rate, electroencephalographicand electromyographic activity, respiration, skin conductance, etc.), we discovered that therhythmic pattern of heart activity was directly associated with the subjective activation ofdistinct emotional states, and that the heart rhythm pattern also reflected changes in emotionalstates, in that it covaried with emotions in real time. We found strong differences between quitedistinct rhythmic beating patterns that were readily apparent in the heart rhythm trace and thatdirectly matched the subjective experience of different emotions. In short, we found that thepattern of the hearts activity was a valid physiological indicator of emotional experience andthat this indicator was reliable when repeated at different times and in different populations.In more specific terms, we examined the natural fluctuations in heart rate, known as heart ratevariability (HRV). HRV is a product of the dynamic interplay of many of the bodys systems.Short-term (beat-to-beat) changes in heart rate are largely generated and amplified by theinteraction between the heart and brain. This interaction is mediated by the flow of neural signalsthrough the efferent and afferent pathways of the sympathetic and parasympathetic branches ofthe autonomic nervous system (ANS). HRV is thus considered a measure of neurocardiacfunction that reflects heartbrain interactions and ANS dynamics.From an activation theory perspective, the focus is on changes in heart rate or in the amountof variability that are expected to be associated with different emotional states. However, whilethese factors can and often do covary with emotions, we have found that it is the pattern of thehearts rhythm that is primarily reflective of the emotional state. Furthermore, we have foundthat changes in the heart rhythm pattern are independent of heart rate: one can have a coherent orincoherent pattern at high or low heart rates. Thus, it is the rhythm, rather than the rate, that ismost directly related to emotional dynamics and physiological synchronization.Emotions and Heart Rhythm PatternsAs mentioned at the outset, researchers have spent much time and effort investigating howemotions change the state and functioning of the bodys systems. While the vast majority of thisbody of work has focused on understanding the pathological effects of negative emotions, recentresearch has begun to balance this picture by investigating the functions and effects of positiveemotions.A synthesis of the voluminous work in developmental neurobiology has shown that themodulation of positive emotions plays a critical role in infant growth and neurologicaldevelopment, which has enormous consequences for later life (Schore, 1994). Other research onadults has documented a wide array of effects of positive emotions on cognitive processing,behavior, and health and well-being. Positive emotions have been found to broaden the scope ofINTEGRAL REVIEWDecember 2009Vol. 5, No. 2perception, cognition, and behavior (Fredrickson, 2001, 2005; Isen, 1999), thus enhancingfaculties such as creativity (Isen, 1998) and intuition (Bolte, Goschke, & Kuhl, 2003). Moreover,the experience of frequent positive emotions has been shown to predict resilience andpsychological growth, (Fredrickson, Tugade, Waugh, & Larkin, 2003) while an impressive bodyof research has documented clear links between positive emotions, health status, and longevity(Blakeslee & Grossarth-Maticek, 1996; Danner, Snowdon, & Friesen, 2001; Medalie &Goldbourt, 1976; Moskowitz, 2003; Ostir, Markides, Black, & Goodwin, 2000; Ostir, Markides,Peek, & Goodwin, 2001;