There has been a long-standing debate on the question of how basic reflexive behaviours in mammals come about. Recently, it has been hypothesized that soft musculoskeletal interactions, such as intrinsic passive dynamics, might play a crucial role in the development of motor control at an early developmental stage. Inspired by the developmental processes, this paper explores a learning framework that enables us to systematically investigate the sensorimotor activity induced in soft musculoskeletal systems, as well as to self-organize a set of decentralized controllers analogue to spinal reflexes in mammals. This paper particularly focuses on three reflexes: the Myotatic reflex, the Reciprocal Inhibition reflex and the Reverse Myotatic reflex. We tested our framework in a simulated pair of soft muscles assembled in an agonist-antagonist arrangement. Our results show that the reflex circuitry as well as the reflex behaviour obtained are consistent with those observed in the mammal spinal cord.