Commentator: Ophelia Deroy (London & RTS project)
It has long been observed that the conscious perception of locomotor space seems to be greatly distorted. Nonetheless perception provides the basis for excellent control of action. Could large and systematic distortions in perceived locomotor space be for the purpose of action control? After all, perceptual sensitivity trumps perceptual accuracy in the control of action – or watchmakers couldn’t use magnifying glasses. I will review a large body of evidence suggesting that many well-documented and systematic biases in the perceptual experience of locomotor space may arise from an angular coding scheme that may provide more efficient motor specification and/or feedback sensitivity for the control of action. Much of the data used in support of the theory was collected or replicated by other labs before the theory was proposed. The critical new empirical observation of the theory is that while angular variables, like egocentric direction, are fundamental to action control, they are found to be grossly and systematically distorted in explicit judgments of perceptual experience. These angular biases are quantitatively consistent with standardly observed distortions in perceived distance. Similar coding efficiency considerations apply to the perceptual scaling of optic flow speed during walking.