In 2017, Capobianco, Morrison, and Wells conducted an experiment to asses how the belief in the importance of thoughts (a negative metacognitive belief) affects people’s stress responses.
75 students (54 women, 21 men) participated in the experiment, and they went through the Trier Social Stress Test, in which they were given a short period to prepare for the upcoming task. They were informed that they would be evaluated by a panel of judges, which helps to create anticipatory stress.
After completing the task, participants entered a recovery phase where they were allowed to relax. This phase was used to measure how quickly participants returned to their baseline physiological and psychological states.
During the experiment, all participants were subjected to a simulated EEG test (EEG: electroencephalogram is a recording of brain activity), where they were told that the EEG could detect negative thoughts.
The experimental group was informed that having a negative thought might result in a burst of loud noise, whereas the control group was told that the loud noise could occur randomly.
The findings indicated no significant differences between the groups in terms of physiological measures, such as skin conductance levels. However, in terms of self-reported measures of stress, those in the experimental group reported higher levels of negative affect and lower levels of positive affect in response to stress, along with sustained low positive affect during the recovery period.
The results suggest that metacognitive beliefs influence both positive and negative affect during and after stress exposure. Even though the physiological stress responses were the same in the two conditions, the perception of stress was significantly different.
If interested, see the reference here.