Chapter 8: Fear, Anxiety, and Stress
During a fear experience, the SNS system is activated, but the PNS system is not. In Levenson et al.’s (1990) study on American participants, fear facial expressions caused an increase in heart rate and skin conductance, a decrease in finger temperature, no change from baseline for muscle activity. In a later study (Levenson et al., 1992), American and Mingankabu participants made a fear facial expression. For both groups, the fear expression resulted in similar increases in heart rate, and small increases to no change for finger temperature. But American participants showed significantly greater increases in skin conductance than Minangkabu participants. Levenson’s studies may be reviewed here.
A recent review (Kreibig, 2010) of physiological changes in fear has found that generally fear causes an increase in heart rate, blood pressure, breathing, skin conductance, as well as, a shortened cardiac pre-ejection period (PEP; review PEP here). Depending on the methodology and the time at which physiology is measured during the fear experience, some fear fear manipulations result in decreased heart rate, which typically occurs earlier in the fear experience. Replicating Levenson and colleagues’ work, fear causes a decrease in finger temperature. Cardiac vagal influence and HRV decrease during fear, indicating loss of parasympathetic influence.