in developmental robotics (weng et al., 2001; lungarella et al., 2003), one aims to investigate the mechanisms that may allow a robot to continuously discover and learn new skills in unknown environments and in a life-long time scale. of particular importance is the fact that the set of these skills and their function(s) are at least partially unknown to the engineer who conceive the robot initially, and are also task-independent. indeed, a desirable feature is that robots should be capable of exploring and developing various kinds of skills that they may re-use later on for tasks that they did not foresee. this is what happens in human children, and this is also why developmental robotics shall import concepts and mechanisms from human developmental psychology.