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the center of the monitor). This fixation spot represented the airport, and the rest of the radar display was the airspace. Each radar display contained several colored equilateral triangles (i.e. planes) of side length 1.15°, where color represented aircraft altitude. Every aircraft was rendered either directly on a node or half-way between nodes, and no aircraft could be within the smallest node. Two aircraft were considered in conflict if they had CH5424802 chemical structure the same color and were on the same node (Fig. 1B). There was never a conflict between aircraft that were lying between nodes. The aircraft parameters (altitude, quadrant location, distance, angular position within the quadrant, RAD001 research buy and state of conflict) were randomly generated to satisfy the following criteria: equal likelihood of 1–4 conflicts per trial, all colors equally likely to be in conflict, all nodes equally likely to be in conflict, at most one conflict per radar display, 1/3 probability of each aircraft positioned between nodes, 1.16° minimum distance between the center of any two planes, at most one plane per node in each quadrant, equal likelihood of angular position within the quadrant, and equal

likelihood for each node in each quadrant to contain a plane. The number of conflicts was kept low in each trial (randomly chosen from one to four) to simulate actual ATC conditions. The conflict angle (i.e. the angle between

the conflicted planes) and the airport and the traffic dispersion (i.e. average distance between each plane and the airport) distributions were equivalent in the high- click here and low-complexity conditions. We used custom code and the Psychophysics Toolbox to create and display the visual stimuli (Brainard, 1997). In the high-complexity condition we presented four planes in each quadrant (for a total of 16 planes per radar display). Here, each quadrant contained at most two planes of the same color. In the low-complexity condition we presented two different colored planes in each quadrant (for a total of eight planes per radar display). In both complexity conditions the colors were balanced in every radar display; that is, each color appeared on the radar display twice for the low-complexity task and four times for the high-complexity task. We ran twenty 45-s-long trials per block, with seven different radar displays per trial, in which each radar display was displayed for 5 s. Thus, we created 140 radar displays per TC condition. All radar displays were viewed by all participants. Participants were instructed to explore each radar display and to report, using a gamepad, the presence or absence of a conflict as quickly as possible (conflict present, right trigger; conflict absent, left trigger).