  In the most extensive robot evolution systems, both the bodies and the brains
of the robots undergo evolution and the brains of 'infant' robots are also
optimized by a learning process immediately after 'birth'. This paper is
concerned with the brain evolution mechanism in such a system. In particular,
we compare four options obtained by combining asexual or sexual brain
reproduction with Darwinian or Lamarckian evolution mechanisms. We conduct
experiments in simulation with a system of evolvable modular robots on two
different tasks. The results show that sexual reproduction of the robots'
brains is preferable in the Darwinian framework, but the effect is the opposite
in the Lamarckian system (both using the same infant learning method). Our
experiments suggest that the overall best option is asexual reproduction
combined with the Lamarckian framework, as it obtains better robots in terms of
fitness than the other three. Considering the evolved morphologies, the
different brain reproduction methods do not lead to differences. This result
indicates that the morphology of the robot is mainly determined by the task and
the environment, not by the brain reproduction methods.
