We tested a dyadic training protocol derived from cognitive and social theories of complex skill acquisition. Forty undergraduates practiced Space Fortress, a video game-like research tool, for 10 sessions of eight practice and two test games. Half of them practiced and tested alone; the others had identical tests but dyadic practice, in which they controlled part of each practice while being interlocked with a partner who controlled the rest. Subjects practiced both parts and their connections by alternating roles and by modeling their partners. Trainer time and resources were half for the dyadic group, and performance was equivalent. We discuss applied and basic implications of this 100% increase in training efficiency.