Physiological Changes

SNS/PNS Activation

In two studies by Levenson and colleagues, participants completed the directed facial action task for anger while physiological measures were taken.  In Levenson et al.’s (1990) study on American participants, anger facial expressions caused an increase in heart rate, finger temperature, and skin conductance, and a no change in muscle activity.  This study also showed the only difference in physiology between anger and fear was that anger resulted in an increase in finger temperature, whereas fear resulted in a decrease in finger temperature. In a later study (Levenson et al., 1992), American and Minangkabau participants made an anger facial expression.  For both groups, making an anger expression resulted in similar increases in heart rate and finger temperature for anger, but American participants showed significantly greater increases in skin conductance than Minangkabau participants.

Kreibig’s review (2010) demonstrates that anger causes similar increases in SNS measures as fear – including heart rate, blood pressure, breathing, and skin conductance, as well as a shortened cardiac pre-ejection period (PEP; review  here).  Taken together, these changes indicate the SNS system is activated.  Findings on finger and head temperature vary; some research has found decreased head and finger temperature, increased head temperature, and unchanged finger temperature (Kreibig, 2010).  These findings on finger temperature do contradict Leveson et al.’s (1990) work described above.  It might be that the directed facial action task, a method which does not have a clear elicitor of anger, might cause these different results for finger temperature.

During an anger experience, heart-rate variability (HRV; pure measure of PNS activity ) decreased or remained the same, indicating PNS deactivation.  One major difference between anger and fear is that fear decreases peripheral resistance, but anger increases peripheral resistance.  Peripheral resistance means the arteries are constricting or tightening, which parallels the bodily tightening in an anger experience. But, combined with other SNS measures, findings depend on the method used to elicit the emotion.  When people are shown angry facial expressions, their heartrate and skin conductance decrease, and their heartrate variability increases.  These findings might occur because viewing anger on another person causes us to feel fear – and the decrease in HR and SCL would be an indicator of orienting.  When viewing angry films, participants show decreased heart rate AND heart-rate variability, suggesting both PNS and SNS systems are not operating.  Kreibig (2010) suggests angry film clips might result in participants focusing and interpreting the film but may not actually result in an anger emotion (again, the issue being the participants are not specifically threatened, but are instead watching another person experience a threat).

Finally, keep in mind that some researchers are leaning toward the idea of several types of anger (Kreibig, 2010).  Approach-anger has shown no change in heart rate, while avoidance-anger results in decreased heart rate.  Anger-out (anger caused by an external agent), resulted in increased heart rate, blood pressure, and other measures of SNS activation.  Whereas, anger-in (anger directed toward the self) resulted in increased heart rate, but no changes in blood pressure. A final note – some emotions experts believe anger toward the self (such as when we fail or hurt another person), actually results in the emotion shame or guilt, not anger.