Keene, TobyPammer, KristenLord, BillShipp, Carol2024-08-052024-08-052047-0894https://hdl.handle.net/1885/733714427Purpose: Previous research has shown that paramedics form intuitive impressions based on limited “pre-arrival” dispatch information and this subsequently affects their diagnosis. However, this observation has never been experimentally studied. Design/methodology/approach: This was an experimental study of 83 Australian undergraduate paramedics and 65 Australian paramedics with median 14 years' experience (Range: 1–32 years). Participants responded to written vignettes in two parts that aimed to induce an intuitive impression by placing participants under time pressure and with a secondary task, followed by a diagnosis made without distraction or time pressure. The vignettes varied the likelihood of Acute Coronary Syndrome (ACS) and measured self-reports of typicality and confidence. Answer fluency, which is the ease with which the answer comes to mind, was also measured. Findings: More participants exposed to the likely pre-arrival vignette recorded a final diagnosis of ACS, than those exposed to unlikely pre-arrival information (0.85 [95%CI: 0.78, 0.90] vs 0.74 [95%CI: 0.66, 0.81]; p = 0.03). This effect was greater in paramedics with more than 14 years' experience (0.94 [95%CI: 0.78, 0.99] vs 0.67 [95%CI: 0.48, 0.81]; p = 0.01). Answer fluency and confidence were associated with the impression, while the impression and confidence were associated with final diagnosis. Practical implications: The authors have experimentally shown that pre-arrival information can affect subsequent diagnosis. The most experienced paramedics were more likely to be affected. Originality/value: This is the first experimental study of diagnostic decision-making in paramedics and paramedic students.application/pdfen-AUparamedicEmergency medical servicesDecision makingDiognosisDual process theory202210.1108/IJES-06-2021-00392024-05-19