The role of positive facial feedback in the stress response

This study investigated whether the old adage "grin and bear it" has proven value by testing how covert and overt manipulation of facial expression influences affective and physiological responses to stress. One hundred and sixty-nine healthy college students were recruited for a "multitasking study," which involved holding chopsticks in the mouth while simultaneously completing two stressful tasks. Participants were randomly assigned to one of the following conditions per the orientation of the chopsticks in their mouths: no smiling (control), Duchenne smiling, or non-Duchenne smiling. Awareness was also manipulated with one half of participants in each smiling condition specifically told to smile and the other half not (N=55 and 57, respectively). State affect changes were assessed at baseline and after each stress task using a short form of the Profile of Mood States, and change scores for positive and negative affect (average PA and NA during each task minus average baseline PA and NA) were used in an analysis of variance to test whether individuals experienced emotional changes concordant with their condition. Group differences in cardiovascular reactivity were examined using analysis of variance with change scores (average cardiovascular activity (heart rate, pulse, and blood pressure) during each task minus average cardiovascular activity at baseline). Repeated measures analysis of variance was employed with pulse and heart rate time points throughout each recovery period to examine group differences in cardiovascular recovery. In all analyses, the following variables were controlled for based on associations with the relevant cardiovascular DV: age; race; sex; body mass index (BMI); baseline perceived stress; sleep; smoking; alcohol use; exercise; condition adherence; perceived task difficulty; reported task facial muscle fatigue; and perceived task stress. Results indicated that non-aware participants in the smiling conditions (M = -0.32) reported less of a decrease in positive affect during a stressful task than individuals in the neutral group (M = -0.65), F(1, 71) = 4.21, p < 0.05, supporting the facial feedback hypothesis (i.e., smiling buffered the negative impact of stress). Generally, smiling had no consistent impact on the stress reactivity of participants as compared to non-smilers across cardiovascular outcomes and tasks. On the other hand, smiling showed widespread effects on cardiovascular recovery, with the smiling groups, regardless of awareness or type of smile, consistently returning closer to baseline levels of cardiovascular activity at the end of the recovery periods following both stress tasks. Practical implications of this relationship between facial feedback, affect, and the stress response are discussed