An egocentric account of the visual guidance of locomotion

The recent series of articles (Lappe et al.1; Wann and Land2) and replies (Harris and Rogers3; Lappe et al.4; Fajen and Warren5) has been useful in drawing out what is and isn't known about the roles of optic flow and perceived egocentric direction in the visual guidance of locomotion. The proposal that perceived egocentric direction has a central role in the guidance of locomotion6 appears to be no longer disputed. Here we wish to clarify some implications of the strong version of this proposal, that locomotion relies exclusively on perceived egocentric direction.