We assess the Situational Intelligence (SQ) component of the MirMe assessment system for 21st century skills. MirMe is an online, game-based psychometric instrument developed by LogicMills. The SQ component measures skills related to decision-making and critical thinking. It does so via AI-driven heuristic engines that deploy analogs of “fast and frugal” heuristics. Approximately 7,000 participants (aged 5 to 92) and 25,000 gameplays were involved in the various validation studies. Results support the conclusion that MirMe’s SQ measures are internally consistent (Cronbach alpha ranging from .71 to .93). Results also suggest that MirMe may be a better predictor of student academic performance (measured by GPA) than A-levels (MirMe r2 = .265, p < .001; A-levels r2 = .209, p < .001). MirMe also appears to predict the kinds of co-curricular activities students participate in both prior to and during university.