Orthogonally Evolved AI to Improve Difficulty Adjustment in Video Games

  • Arend HintzeEmail author
  • Randal S. Olson
  • Joel Lehman
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 9597)


Computer games are most engaging when their difficulty is well matched to the player’s ability, thereby providing an experience in which the player is neither overwhelmed nor bored. In games where the player interacts with computer-controlled opponents, the difficulty of the game can be adjusted not only by changing the distribution of opponents or game resources, but also through modifying the skill of the opponents. Applying evolutionary algorithms to evolve the artificial intelligence that controls opponent agents is one established method for adjusting opponent difficulty. Less-evolved agents (i.e., agents subject to fewer generations of evolution) make for easier opponents, while highly-evolved agents are more challenging to overcome. In this publication we test a new approach for difficulty adjustment in games: orthogonally evolved AI, where the player receives support from collaborating agents that are co-evolved with opponent agents (where collaborators and opponents have orthogonal incentives). The advantage is that game difficulty can be adjusted more granularly by manipulating two independent axes: by having more or less adept collaborators, and by having more or less adept opponents. Furthermore, human interaction can modulate (and be informed by) the performance and behavior of collaborating agents. In this way, orthogonally evolved AI both facilitates smoother difficulty adjustment and enables new game experiences.


Difficulty adjustment Coevolution Evolutionary computation Markov Networks 



We would like to thank Chris Adami for insightful comments and discussion of the project.


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Copyright information

© Springer International Publishing Switzerland 2016

Authors and Affiliations

  1. 1.Michigan State UniversityMichiganUSA
  2. 2.University of PennsylvaniaPennsylvaniaUSA
  3. 3.IT University of CopenhagenCopenhagenDenmark

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