Study objectivesInattentional blindness is the psychological phenomenon of inability to see the unexpected even if it is in plain view. We hypothesized that anesthesiologists may overlook unexpected intraoperative events whereas medical students, lacking in intraoperative monitoring experience and knowledge, may be more likely to notice such events. DesignA simulation study using a video of a simulated septic patient undergoing abdominal surgery. SettingA large academic center. Participants31 certified anesthesiologists and 46 upper-year medical students. InterventionsNone. Participants watched a video of a simulated surgery and scored the abnormalities they saw. MeasurementsThese abnormalities included abnormal physiologic parameters consistent with the condition of the simulated septic patient, and two unexpected but plausible events: head movement and a leaky central line catheter. Main resultsStudents were significantly more likely than anesthesiologists to notice head movement (p<0.001).