A final objection to the reafference theory concerns the end product of adaptation to ORDs. According to the theory, adaptation occurs when subjects learn new rules of sensorimotor dependence that govern how actions affect sensory inputs. There is a significant body of evidence, however, that much, if not all, adaptation rather occurs at the proprioceptive level. Stratton, summarizing the results of his experiment on mirror-based optical rearrangement, wrote: