The reafference theory was also significantly motivated by studies of how subjects adapt to devices that alter the relationship between the distal visual world and sensory input by rotating, reversing, or laterally displacing the retinal image (for helpful guides to the literature on this topic, see Rock 1966; Howard &amp; Templeton 1966; Epstein 1967; and Welch 1978). We will refer to these as optical rearrangement devices (or ORDs for short).