RT Journal Article
SR Electronic
T1 Dissociable effects of visual crowding on the perception of colour and motion
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 639450
DO 10.1101/639450
A1 John A. Greenwood
A1 Michael J. Parsons
YR 2019
UL http://biorxiv.org/content/early/2019/05/17/639450.1.abstract
AB Our ability to recognise objects in peripheral vision is fundamentally limited by crowding [1–3], the deleterious effect of clutter that disrupts features ranging from orientation [4] and colour [5, 6] to motion [7] and depth [8, 9]. Prior research is equivocal on whether this reflects a singular process that disrupts all features simultaneously or multiple processes that affect each independently [5, 10–12]. We examined crowding for colour and motion, two features that allow a strong test of feature independence. ‘Cowhide’ stimuli were presented 15 degrees in peripheral vision, either in isolation or surrounded by flankers to give crowding. Observers reported either the target hue (blue/purple) or its direction (clockwise/counter-clockwise from upwards). We first established that both dimensions show systematic crowded errors (predominantly biased towards the flanker identities) and selectivity for target-flanker similarity (with reduced crowding for dissimilar elements). The multiplicity of crowding was then tested with observers identifying both features: a singular object-selective mechanism predicts that when crowding is weak in one dimension and strong for the other that crowding should be all-or-none for both. In contrast, when crowding was weak for colour and strong for motion, errors were reduced for colour but remained for motion, and vice versa with weak motion and strong colour crowding. This double dissociation follows the predictions of independent crowding processes, suggesting that crowding disrupts vision in a feature-specific manner. The ability to recognise one aspect of a cluttered scene (like colour) thus offers no guarantees for the correct recognition of other aspects (like motion).