The ESP method for evolving virtual creatures  consisted of
an encapsulation mechanism to preserve learned skills, a
human-designed syllabus to build higher-level skills by
combining lower-level skills systematically, and a pandemonium
mechanism to resolve conflicts between encapsulated skills in
a single creature's brain. Previous work with ESP showed that
it is possible to evolve much more complex behavior than
before, even when fundamental morphology (i.e., skeletal
segments and joints) was evolved only for the first skill.
This paper introduces a more general form of ESP in which full
morphological development can continue beyond the first skill,
allowing creatures to adapt their morphology to multiple
tasks. This extension increases the variety and quality of
evolved creature results significantly, while maintaining the
original ESP system's ability to incrementally develop complex
behaviors from a sequence of simpler learning tasks. In the
future, this method should make it possible to build EVCs with
complex and believable behavior.
 Dan Lessin, Don Fussell, and Risto Miikkulainen.
Open-Ended Behavioral Complexity for Evolved Virtual
Creatures. GECCO 2013.