Abstract: Aims to develop a new empirical method for assessing the similarity of mental models in surgery, focusing on laparotomy; to begin the process of validation of the new approach; and to demonstrate how the new approach could be used in clinical practice. Develops a software application (Momento) to sort key tasks in order to capture the information on mental models regarding task sequence and responsibility. Asks 20 6-person operating room (OR) teams, each comprising 3 sub-teams consisting of anaesthesia, surgery and nursing, to complete Momento prior to 2 simulated emergency laparotomies. Suggests the Momento approach could be used to improve teamwork in OR.