The key argumentation for the need of motor synergies when learning a novel sensorimotor task was always: the dimension needs to be reduced - high dimensions can not be explored. True – for exhaustive exploration. False – if goals can be used to scaffold exploration as I show with my work on goal babbling. So maybe motor synergies are not really needed?
What comes on top is: I show in this contribution that motor synergies are distally observable during goal babbling, meaning that when someone searches for motor synergies - applying the standard experimental measures for behavioural experiments - in a system performing goal babbling, one will find motor synergies. This goes down to a rigorous proof for linear domains.
Hence, goal babbling can explain evidence on motor synergies, with no motor synergies being inside, but just performing efficient exploration in high dimensions right away.
Matthias Rolf and Minoru Asada. "Motor synergies are naturally observed during goal babbling". IROS 2013 Workshop: Cognitive Neuroscience Robotics, Tokyo, 11/2013.
"Abstract — Motor synergies describe joint activations of muscles or motors during sensorimotor tasks. Hard-wired synergies have been discusses to facilitate and ease motor control at the levels of mechanical actuation of biological systems and spinal motor control. Long-lasting debates additionally issue adaptive synergies as mechanism for learning in sensorimotor domains, such as a “freezing and freeing” of degrees of freedom in order to reduce the dimension of sensorimotor tasks. This paper discusses the terms of synergies and DOF freezing in the light of recent work on Goal Babbling. We discuss conceptual, experimental, and theoretic evidence showing that synergies and DOF freezing must be distally observable phenomena during goal babbling. We therefore argue that synergies might be viewed as an effect rather than the mechanism of efficient sensorimotor learning."