This two-volume set LNCS 10915 and 10916 constitutes the refereed proceedings of the 12h International Conference on Augmented Cognition, AC 2018, held as part of the 20th International Conference on Human-Computer Interaction, HCII 2018, in Las Vegas, NV, USA in July 2018. The 1171 papers presented at HCII 2018 conferences were carefully reviewed and selected from 4346 submissions. The papers cover the entire field of human-computer interaction, addressing major advances in knowledge and effective use of computers in a variety of applications areas. The papers in this volume are organized in the following topical sections: context aware adaption strategies in augmented cognition, brain sensors and measures for operational environments, artificial intelligence and machine learning in augmented cognition, augmented cognition in virtual and mixed reality.