Summary with the article: The autonomic nervous system and emotion - Levenson (2014)

Coherence and specificity in the relation between the autonomic nervous system and emotion

There is no doubt that the autonomic nervous system plays an important role in generating, expressing, experiencing and recognizing different emotions. However, research has found more controversies rather than consensus in the relationship between the different aspects of the autonomic nervous system and emotion.

One of these controversies is about the degree of the extent to which the autonomic nervous response in emotions is organized and coordinated (also referred to as coherence). There are two types of coherence. The first is coherence lies within the autonomic nervous system, which consists of cardiac and vascular responses. The second coherence is between the autonomic nervous system and other systems responsible for emotion response, such as facial expressions. Another important controversy is about the degree of autonomic nervous system specificity in emotion, an issue also referred to as the differences in autonomic nervous system responses for particular emotions.

Research on the association between different aspects of the autonomic nervous system and emotion faces many challenges. First of all, the autonomic nervous system responds to many (non-emotional) signals. Therefore, a change in activity within the system isn’t always caused by emotion. Secondly, bodily reactions associated with emotion, for example dilated pupils when experiencing fear, could also be caused by a homeostatic reaction, for example adjusting the pupil to the accessible amount of light. And finally, it has shown that it is nearly impossible to differentiate between responses caused by emotion or by personality.

Misconceptions on the role of the autonomic nervous system on emotion

There are several misconceptions concerning the autonomic nervous system on emotion:

The autonomic nervous system consists of two branches: the sympathetic nervous system and the parasympathetic nervous system. It is commonly thought that the sympathetic nervous system is the more activating system of the two, but this isn’t always the case.

Measuring the variability in heart rate doesn’t say anything on the activity of the entire parasympathetic nervous system.

It is thought that the most important role of the autonomic nervous system is arranging activity (both increased and decreased) in target organs. However, this is not the case.

Different models of emotion

The cognitive model of emotion states that emotions results from processes in higher brain centres (top-down view). Evolutionary/functionalist models state that bodily responses influence the subjective experience of emotion (bottom-up view). It is thought that during evolution different emotions were preserved as a generalized solution for common problems and therefore influenced our behaviour. The subjective emotional experience is not the most important feature of emotion, but come up after one detects bodily changes. It is claimed that different emotions cause different pattern of bodily reactions and therefore are recognizable to us.

The evolutionary/functionalist models suggest that coherence and specificity are two important variants of autonomic nervous system patterning. Back in the days it was thought that emotions lead to chaos, but within these models it is thought that emotions lead to coordinated and effective responses to challenges and has an organizing function. In order to assess and quantify coherence, three criteria must be met. The first is that subjective, behavioural and physiological responses need to be measured over time. Secondly, different temporal characteristics of various systems responding to emotion need to be accounted for. Finally, the degree of coherence must be measured when participants reach their peaks in experiencing a strong emotion. Many studies on coherence do not meet these three criteria and found low coherence across emotion response systems. The one study that did found high evidence for coherence across response systems. This is clearly a topic for future research.

The evolutionary/functionalist models also suggest that different emotions have different autonomic nervous system activity to help deal efficiently with possible obstacles in survival. Challenges in research are that humans often experience many different emotions during the day and there is no guarantee that a particular stimulus will elicit the targeted emotion. Many studies do not verify emotions and assume that the emotion evoked was the emotion they targeted. Secondly, many emotions evoked in a laboratory are subject to appraisal, which makes it possible for someone to adjust a high-intensity emotion to a low-intensity emotion. Another challenge is that many studies are prone to assess fairly easy autonomic nervous system responses, that do no justice to the dynamic nature of the autonomic nervous system. It is thought that eventually evidence will be found for specificity of at least four of the six basic emotions, but because of all the methodological challenges, this has not yet been found.