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Perceiving Emergencies: Laypeople's Judgement, Stress, and Performance in Traumatic Bleeding
Linköping University, Department of Computer and Information Science, Human-Centered Systems. Linköping University, Faculty of Arts and Sciences.ORCID iD: 0000-0002-4416-2525
2026 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Att uppfatta en nödsituation : Lekmäns bedömning, stress och prestation vid traumatisk blödning (Swedish)
Abstract [en]

Traumatic hemorrhage is one of the leading causes of preventable death worldwide, and early hemorrhage control is critical for survival. In many emergency situations, the first individuals present are medical laypeople rather than professional responders. These immediate responders face extreme time pressure, uncertainty, and stress, yet are increasingly expected to initiate life-saving interventions such as hemorrhage control. Despite widespread implementation of civilian hemorrhage control initiatives, including the Stop the Bleed (STB) campaign, limited empirical knowledge exists regarding how laypeople perceive traumatic injuries, interpret severity, and perform hemorrhage control under realistic conditions. Training programs have largely been informed by clinical and military perspectives, with comparatively little grounding in cognitive science or human factors.

This thesis examines the cognitive, perceptual, and affective mechanisms underlying laypeople’s responses to life-threatening bleeding. Drawing on theories from cognitive science and human factors, most notably Brunswik’s lens model, naïve theories, and stress theory, the thesis conceptualizes medical emergencies as epistemic events shaped by uncertainty, probabilistic cues, and human sensemaking. From this perspective, recognizing and responding to hemorrhage is not solely a matter of technical skill acquisition, but of judgment under uncertainty, cue interpretation, and performance under stress.

The thesis consists of six papers. Five papers employing experimental, simulation-based methods, and one literature review. The included studies investigate how factors such as stress, exposure to blood, and visual characteristics of injuries influence laypeople’s ability to recognize hemorrhage, estimate blood loss, prioritize victims, and perform bleeding control interventions. Several studies directly assess performance rather than relying on surrogate outcomes such as confidence or intention, thereby addressing a key limitation in existing bleeding control research.

Across the included papers, the results demonstrate that laypeople’s hemorrhage control performance is systematically affected by cognitive and environmental constraints. Stress and salient trauma cues can impair both perceptual judgment and motor performance, while mismatches between perceived severity and actual injury severity highlight limitations in current training approaches. The findings suggest that conventional training models may insufficiently account for how laypeople attend to, interpret, and act upon probabilistic cues in emergency contexts.

By integrating empirical findings with theory-informed analysis, this thesis contributes to a more cognitively grounded understanding of layperson emergency response. The work advances knowledge on how hemorrhage control training can be better aligned with human perceptual and decision-making processes, and offers implications for the design of more effective, realistic, and transferable training for the general public. Ultimately, this research aims to support training practices that enhance early intervention capacity and societal resilience in medical emergencies.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2026. , p. 137
Series
Linköping Studies in Arts and Sciences, ISSN 0282-9800 ; 940
Keywords [en]
Conceptual change, First aid, Hemorrhage, Judgement, Perception, Stress
Keywords [sv]
Begreppsförändring, Första hjälpen, Blödning, Bedömning, Perception, Stress
National Category
Applied Psychology
Identifiers
URN: urn:nbn:se:liu:diva-223744DOI: 10.3384/9789181185973ISBN: 9789181185966 (print)ISBN: 9789181185973 (electronic)OAI: oai:DiVA.org:liu-223744DiVA, id: diva2:2058982
Public defence
2026-06-05, Ada Lovelace, B-building, Campus Valla, Linköping, 09:00 (English)
Opponent
Supervisors
Note

Funding: Part of this work have been funded by the Swedish Civil Defence and Resilience Agency (Swedish: Myndigheten för civilt försvar, MCF), former Swedish Civil Contingencies Agency (Swedish: Myndigheten för samhällskydd och beredskap, MSB), (2018-12395 MSB). Additionally, part of this work has also been funded by the ALF Grant, Region Östergötland, and by the National Board of Health and Welfare (Swedish: Socialstyrelsen).

Available from: 2026-05-11 Created: 2026-05-11 Last updated: 2026-05-11Bibliographically approved
List of papers
1. The Effects of Stress on Tourniquet Application and CPR Performance in Layperson and Professional Civilian Populations
Open this publication in new window or tab >>The Effects of Stress on Tourniquet Application and CPR Performance in Layperson and Professional Civilian Populations
2023 (English)In: Human Factors, ISSN 0018-7208, E-ISSN 1547-8181, Vol. 65, no 3, p. 496-507, article id 00187208211021255Article in journal (Refereed) Published
Abstract [en]

Objective The purpose of this study was to compare laypeoples and professional first responders ability to perform tourniquet application and cardiopulmonary resuscitation (CPR) during calm and stressful circumstances. Background Life-threatening bleeding is a major cause of death that could be prevented by fast and appropriate first aid interventions. Therefore, laypeople are now being trained in bleeding control skills, transforming them from bystanders to immediate responders. However, critics have questioned whether laypeople are able to perform during more stressful conditions. Method Twenty-four laypersons and 31 professional first responders were tested in two conditions: a calm classroom scenario and a stressful scenario consisting of paintball fire and physical exertion. Stress and workload were assessed along with task performance. Results The experimental manipulation was successful in terms of eliciting stress reactions. Tourniquet application performance did not decline in the stressful condition, but some aspects of CPR performance did for both groups. First responders experienced higher task engagement and lower distress, worry and workload than the laypeople in both the calm and stressful conditions. Conclusion Stress did not affect first responders and laypeople differently in terms of performance effects. Stress should therefore not be considered a major obstacle for teaching bleeding control skills to laypeople. Application Tourniquet application can be taught to laypeople in a short amount of time, and they can perform this skill during stress in controlled settings. Concerns about laypeoples ability to perform under stress should not exclude bleeding control skills from first aid courses for civilian laypeople.

Place, publisher, year, edition, pages
SAGE PUBLICATIONS INC, 2023
Keywords
tourniquet; stress; first aid; laypeople; first responders
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:liu:diva-176466 (URN)10.1177/00187208211021255 (DOI)000657084000001 ()34039045 (PubMedID)2-s2.0-85106597803 (Scopus ID)
Note

Funding Agencies|Swedish Civil Contingencies Agency; ALF Grant, Region Ostergotland

Available from: 2021-06-15 Created: 2021-06-15 Last updated: 2026-05-11Bibliographically approved
2. The Effect of Presence of Blood on Medical Laypeople’s Ability to Perform First Aid for Massive Bleeding
Open this publication in new window or tab >>The Effect of Presence of Blood on Medical Laypeople’s Ability to Perform First Aid for Massive Bleeding
2022 (English)In: Proceedings of the Human Factors and Ergonomics Society Annual Meeting, Sage Publications, 2022, Vol. 66, p. 251-255Conference paper, Published paper (Refereed)
Abstract [en]

There are currently several educational initiatives to teach first aid courses for medical laypeople, such as the Stop the Bleed campaign. Although much research on educational initiatives has been conducted, there are still factors that remain unexplored, such as the potential effects of blood itself on laypeople’s first aid performance and educational experience. This study investigates such potential effects for performance of the first aid techniques tourniquet application and wound packing, in relation to individual differences in disgust sensitivity and medical fear of blood. The results show that the presence of blood will increase the time a medical layperson takes to apply a tourniquet and pack a wound but does not affect the quality of the aid. Additionally, the disgust sensitivity of the medical layperson was found to predict an increase in application time for the wound packing task, but not the tourniquet application task, when blood was present.

Place, publisher, year, edition, pages
Sage Publications, 2022
Series
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, ISSN 2169-5067, E-ISSN 1071-1813 ; 66
National Category
Applied Psychology
Research subject
Disaster Medicine
Identifiers
urn:nbn:se:liu:diva-197329 (URN)10.1177/1071181322661061 (DOI)2-s2.0-85164098852 (Scopus ID)
Conference
Human Factors and Ergonomics Society Annual Meeting
Available from: 2023-08-31 Created: 2023-08-31 Last updated: 2026-05-11
3. Visual estimates of blood loss by medical laypeople: Effects of blood loss volume, victim gender, and perspective
Open this publication in new window or tab >>Visual estimates of blood loss by medical laypeople: Effects of blood loss volume, victim gender, and perspective
Show others...
2020 (English)In: PLOS ONE, E-ISSN 1932-6203, Vol. 15, no 11, article id e0242096Article in journal (Refereed) Published
Abstract [en]

A severe hemorrhage can result in death within minutes, before professional first responders have time to arrive. Thus, intervention by bystanders, who may lack medical training, may be necessary to save a victims life in situations with bleeding injuries. Proper intervention requires that bystanders accurately assess the severity of the injury and respond appropriately. As many bystanders lack tools and training, they are limited in terms of the information they can use in their evaluative process. In hemorrhage situations, visible blood loss may serve as a dominant cue to action. Therefore, understanding how medically untrained bystanders (i.e., laypeople) perceive hemorrhage is important. The purpose of the current study was to investigate the ability of laypeople to visually assess blood loss and to examine factors that may impact accuracy and the classification of injury severity. A total of 125 laypeople watched 78 short videos each of individuals experiencing a hemorrhage. Victim gender, volume of blood lost, and camera perspective were systematically manipulated in the videos. The results revealed that laypeople overestimated small volumes of blood loss (from 50 to 200 ml), and underestimated larger volumes (from 400 to 1900 ml). Larger volumes of blood loss were associated with larger estimation errors. Further, blood loss was underestimated more for female victims than male victims and their hemorrhages were less likely to be classified as life-threatening. These results have implications for training and intervention design.

Place, publisher, year, edition, pages
PUBLIC LIBRARY SCIENCE, 2020
National Category
Other Medical Sciences not elsewhere specified
Identifiers
urn:nbn:se:liu:diva-172075 (URN)10.1371/journal.pone.0242096 (DOI)000593948000058 ()33180812 (PubMedID)2-s2.0-85096062693 (Scopus ID)
Note

Funding Agencies|Swedish Civil Contingencies Agency [2018-12395 MSB]

Available from: 2020-12-28 Created: 2020-12-28 Last updated: 2026-05-11
4. Laypeople perception and interpretation of simulated life-threatening bleeding: a controlled experimental study
Open this publication in new window or tab >>Laypeople perception and interpretation of simulated life-threatening bleeding: a controlled experimental study
Show others...
2021 (English)In: BMC Emergency Medicine, E-ISSN 1471-227X, Vol. 21, no 1, article id 100Article in journal (Refereed) Published
Abstract [en]

Introduction First aid performed by immediate responders can be the difference between life and death in the case of trauma with massive bleeding. To develop effective training programs to teach bleeding control to laypersons, it is important to be aware of beliefs and misconceptions people hold on bleeding and severity of bleeding situations. Method A controlled study was conducted in which 175 American college students viewed 78 video clips of simulated bleeding injuries. The volume of blood present (between 0 and 1900 ml), rate of blood flow, and victim gender were systematically varied within participants. Participants were asked to rate injury severity, indicate the appropriate first aid action, and estimate the amount of time until death for the victim. Results Though the Stop the Bleed (R) campaign recommends training laypeople to treat 165 ml of blood loss as life threatening, participants largely rated this volume of blood loss as minimal, mild, or moderate and estimated that the victim had just under one hour to live. Increased blood loss was associated with increased recommendations to use a tourniquet. However, in the 1900 ml conditions, participants still estimated that victims had around 22 minutes to live and approximately 15% recommended direct pressure as the intervention. Severity ratings and recommendations to use a tourniquet were also higher for the male victim than the female victim. Conclusions Injury classification, intervention selection, and time to death-estimations revealed that training interventions should connect classifications of blood loss to appropriate action and focus on perceptions of how much time one has to respond to a bleeding. The study also revealed a gender related bias in terms of injury classification and first aid recommendations. Bleeding control training programs can be designed to address identified biases and misconceptions while building on existing knowledge and commonly used terminology.

Place, publisher, year, edition, pages
BMC, 2021
Keywords
Blood loss estimation; Bleeding control; Training; Laypeople; Immediate responder
National Category
Anesthesiology and Intensive Care
Identifiers
urn:nbn:se:liu:diva-179428 (URN)10.1186/s12873-021-00496-2 (DOI)000693076900001 ()34481458 (PubMedID)2-s2.0-85114371111 (Scopus ID)
Note

Funding Agencies|Swedish Civil Contingencies Agency; Linkoping University

Available from: 2021-09-22 Created: 2021-09-22 Last updated: 2026-05-11
5. Prioritization of victims with traumatic bleeding among medical laypeople – An experimental study
Open this publication in new window or tab >>Prioritization of victims with traumatic bleeding among medical laypeople – An experimental study
2025 (English)In: Human Factors in Healthcare, ISSN 2772-5014, Vol. 8, article id 100116Article in journal (Refereed) Published
Abstract [en]

Introduction

Immediate responders, or medical laypeople, are believed to be a useful resource in trauma response. However, efficiently providing first aid interventions such as bleeding control, in scenarios with multiple casualties require prioritization among several injured victims. This study aims to explore how medical laypeople prioritize among victims in forced choice scenarios.

Methods

A controlled online experiment was conducted where participants were presented with 276 image pairs of victims with simulated injuries. The amount of blood loss (100 ml, 500 ml, 900 ml), gender (man, woman), skin color (light, dark), facial expression (unconscious, in pain) and wound visibility (visible, covered) was manipulated across the image stimuli.

Results429 participants completed the experiment. The findings show that victims with greater blood loss are more likely to be prioritized than victims with lower blood loss. Response time indicates that blood loss is likely to be a major factor while prioritizing victims. Victim gender, skin color, facial expression and wound visibility all significantly affect prioritization to some extent.

ConclusionThis study shows that apparent prioritization biases are to be expected in the prehospital setting during medical emergencies for medical laypeople. Such biases could be mitigated through training and education.

Place, publisher, year, edition, pages
Elsevier BV, 2025
Keywords
Decision-making; Hemorrhage; Trauma; Immediate responder; Prioritization
National Category
Applied Psychology
Identifiers
urn:nbn:se:liu:diva-219951 (URN)10.1016/j.hfh.2025.100116 (DOI)001627770800001 ()2-s2.0-105022170489 (Scopus ID)
Funder
Swedish National Board of Health and Welfare
Available from: 2025-12-11 Created: 2025-12-11 Last updated: 2026-05-11

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