Yasutake Takahashi Yoshihiro Tamura Minoru Asada Spiral Development of Behavior Acquisition and Recognition Based on State Value. 343-354 2008 RoboCup http://dx.doi.org/10.1007/978-3-642-02921-9_30 conf/robocup/2008 db/conf/robocup/robocup2008.html#TakahashiTA08