Crowding and the tilt illusion: toward a unified account.

Crowding, the difficult identification of peripherally viewed targets amidst similar distractors, has been explained as a compulsory pooling of target and distractor features. The tilt illusion, in which the difference between two adjacent gratings' orientations is exaggerated, has also been explained by pooling (of Mexican-hat-shaped population responses). In an attempt to establish both phenomena with the same stimuli--and account for them with the same model--we asked observers to identify (as clockwise or anticlockwise of vertical) slightly tilted targets surrounded by tilted distractors. Our results are inconsistent with the feature-pooling model: the ratio of assimilation (the tendency to perceive vertical targets as tilted in the same direction as slightly tilted distractors) to repulsion (the tendency to perceive vertical targets as tilted away from more oblique distractors) was too small. Instead, a general model of modulatory lateral interaction can better fit our results.

[1]  J. Gibson.  Adaptation, after-effect, and contrast in the perception of tilted lines. II. Simultaneous contrast and the areal restriction of the after-effect. , 1937 .

[2]  H. Burian,et al.  A study of separation difficulty. Its relationship to visual acuity in normal and amblyopic eyes. , 1962, American journal of ophthalmology.

[3]  C. Blakemore,et al.  Lateral Inhibition between Orientation Detectors in the Human Visual System , 1970, Nature.

[4]  R Over,et al.  Orientation illusion and masking in central and peripheral vision. , 1972, Journal of experimental psychology.

[5]  H. Bouma,et al.  Eccentric vision: Adverse interactions between line segments , 1976, Vision Research.

[6]  R. Jacobs.  Visual resolution and contour interaction in the fovea and periphery , 1979, Vision Research.

[7]  Ian P. Howard,et al.  Human visual orientation , 1982 .

[8]  S. Klein,et al.  Vernier acuity, crowding and cortical magnification , 1985, Vision Research.

[9]  C. Gilbert,et al.  Improvement in visual sensitivity by changes in local context: Parallel studies in human observers and in V1 of alert monkeys , 1995, Neuron.

[10]  D. Fitzpatrick.  The functional organization of local circuits in visual cortex: insights from the study of tree shrew striate cortex. , 1996, Cerebral cortex.

[11]  S Baldassi,et al.  Are there separate first-order and second-order mechanisms for orientation discrimination? , 2000, Vision Research.

[12]  M. Carrasco,et al.  Characterizing visual performance fields: effects of transient covert attention, spatial frequency, eccentricity, task and set size. , 2001, Spatial vision.

[13]  U. Polat,et al.  Contrast response characteristics of long-range lateral interactions in cat striate cortex , 2001, Neuroreport.

[14]  J. Lund,et al.  Compulsory averaging of crowded orientation signals in human vision , 2001, Nature Neuroscience.

[15]  C. Tyler,et al.  Lateral modulation of contrast discrimination: flanker orientation effects. , 2002, Journal of vision.

[16]  Zhaoping Li.  A saliency map in primary visual cortex , 2002, Trends in Cognitive Sciences.