Although　human　problem　solving　has　been　investigated　in　a　behavior　based　approach,　it　has　been　recognized　that　ignoring　what　goes　on　in　human　brain　and　focusing　instead　on　behavior　has　been　a　large　impediment　to　understand　how　human　being　does　complex　adaptive,　distributed　problem　solving　and　reasoning.　In　the　paper,　we　propose　a　methodology　for　investigating　human　problem　solving　process　by　combining　ERP　mental　arithmetic　tasks,　as　a　case　study,　with　multi-aspect　data　analysis.　Preliminary　results　show　the　usefulness　of　our　methodology.　©　Springer-Verlag　Berlin　Heidelberg　2007.