Heading perception and the allocation of attention

A central theme in previous studies of heading judgements has been whether the retinal flow field can be decomposed to recover the translation compone nt of locomotion when flow also contains the effects of gaze rotation. We e xplored not just the effect of moving gaze, but also moving attention away from the locomotor path by presenting the case of fixating a road sign and completing different attentional tasks during locomotion. Heading errors in creased significantly with attentional load, in the absence of extra-retina l gaze information. When we introduced extra-retinal gaze information with the same tasks this resulted in a significant improvement in heading judgem ents. These results lead us to question whether the decomposition argument translates to real-world judgements of locomotor heading. If observers need to closely attend to roadside information it seems that decomposition is i neffective, whereas if they have the latitude to alternate gaze it is unnec essary. (C) 2000 Elsevier Science Ltd. All rights reserved.