The Social Regulation of Threat-related Vigilance and Arousal

Primary outcomes

1. Vigilance Related Eye Movements - Number of Eye Fixations

   Time frame: Collected from minute 15 to minute 45 of study participation, approximately

   Participants will view 15 pictures of natural environmental scenes for 10 seconds per image. We will use an eye tracker to examine the number of eye fixations per scene. A greater number of fixations during the 10 second presentation of a scene would indicate greater vigilance.

2. Vigilance Related Eye Movements - Visual Scanning

   Time frame: Collected from minute 15 to minute 45 of study participation, approximately

   Participants will view 15 pictures of natural environmental scenes for 10 seconds per image. We will use an eye tracker to examine the proportion of the scene that they look at (fixate on) out of approximately 80 possible sectors. A greater proportion of the scene they fixate on would indicate greater vigilance.

3. Threat-Related Physiological Arousal - Pupil Dilation

   Time frame: Collected from minute 45 to minute 75 of study participation, approximately

   Participants will view a series of visual cues (either an 'X' or an 'O') where an 'X' signals a possible (20% probability) aversive auditory stimulus (human scream). We will examine pupil dilation during the task in order to measure arousal in response to uncertain threat. We will calculate average pupil dilation during the wait period after threat cues (X) and after safety cues (O). We will subtract average pupil dilation after safety cues from threat cues to create an index of threat-related arousal. Greater pupil dilation (for threat minus safety cues) would indicate greater threat-related arousal.