Year
2025
Season
Spring
Paper Type
Master's Thesis
College
College of Arts and Sciences
Degree Name
Master of Science in Psychological Science (MSPS)
Department
Psychological and Brain Sciences
NACO controlled Corporate Body
University of North Florida. Department of Psychological and Brain Sciences
Committee Chairperson
Dr. Lori Lange
Second Advisor
Dr. Gregory Kohn
Department Chair
Dr. Lori Lange
Abstract
This pilot study examined physiological markers of the human freeze response during exposure to threat and safety-based video stimuli. The freeze response is an adaptive defense mechanism characterized by reduced heart rate and heightened sympathetic arousal (Roelofs, 2017; Hagenaars et al., 2014; Sagliano et al., 2014; Hermans et al., 2013). 20 university students were randomly assigned to view either a threatening or safety-based video clip while heart rate and electrodermal activity (EDA) were recorded using Biopac Bionomadix wireless systems. Trauma severity and PTSD symptomatology were assessed through validated self-report measures (BTQ; Schnurr et al., 1999), (PCL-5; Weathers et al., 2013). Although traditional ANCOVA analyses did not reveal statistically significant group differences, moderate effect sizes suggested trends toward elevated sympathetic activity. Additionally, correlation analysis did not reveal any significant association between trauma severity and PTSD severity with physiological responses regardless of the video condition. Time-segmented analyses revealed brief autonomic shifts, particularly during the early moments of video onset, indicative of an orienting response. These patterns were obscured in condition-level averaging, emphasizing the value of segmented physiological analysis in freeze response research. Although the study was underpowered, it demonstrated the basis for capturing subtle biobehavioral changes through physiological recording and segmentation analysis. Future research should use larger, trauma-diverse samples, use subjective experience metrics, and employ machine learning approaches to confirm patterns in physiological data. Findings from this pilot contribute to an emerging understanding of how trauma influences defensive states and highlight the potential for refined methodologies in psychophysiological research.
Suggested Citation
McCarthy, Ula, "A pilot study of the freeze response: Physiological markers under threat versus safety video conditions" (2025). UNF Graduate Theses and Dissertations. 1339.
https://digitalcommons.unf.edu/etd/1339