Compulsory averaging of crowded orientation signals in human vision

A shape can be more difficult to identify when other shapes are near it. For example, when several grating patches are viewed parafoveally, observers are unable to report the orientation of the central patch. This phenomenon, known as 'crowding,' has historically been confused with lateral masking, in which one stimulus attenuates signals generated by another stimulus. Here we show that despite their inability to report the orientation of an individual patch, observers can reliably estimate the average orientation, demonstrating that the local orientation signals are combined rather than lost. Our results imply that crowding is distinct from ordinary masking, and is perhaps related to texture perception. Under crowded conditions, the orientation signals in primary visual cortex are pooled before they reach consciousness.

[1]  D. Hubel,et al.  Receptive fields of single neurones in the cat's striate cortex , 1959, The Journal of physiology.

[2]  D. M. Green,et al.  Signal detection theory and psychophysics , 1966 .

[3]  H. BOUMA,et al.  Interaction Effects in Parafoveal Letter Recognition , 1970, Nature.

[4]  Gerald Westheimer,et al.  Temporal and spatial interference with vernier acuity , 1975, Vision Research.

[5]  E DITORS,et al.  Who and what. , 1975, Pediatrics.

[6]  S P McKee,et al.  Interference with line-orientation sensitivity. , 1976, Journal of the Optical Society of America.

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

[8]  Dennis M. Levi,et al.  Hyperacuity and amblyopia , 1982, Nature.

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

[10]  B Julesz,et al.  "Where" and "what" in vision. , 1985, Science.

[11]  B M Dow,et al.  The mapping of visual space onto foveal striate cortex in the macaque monkey , 1985, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[12]  M. Morgan,et al.  Perceived diagonals in grids and lattices , 1989, Vision Research.

[13]  M J Morgan,et al.  Evidence for positional coding in hyperacuity. , 1990, Journal of the Optical Society of America. A, Optics and image science.

[14]  P Perona,et al.  Preattentive texture discrimination with early vision mechanisms. , 1990, Journal of the Optical Society of America. A, Optics and image science.

[15]  Denis G. Pelli,et al.  Accurate control of contrast on microcomputer displays , 1991, Vision Research.

[16]  U. Polat,et al.  The architecture of perceptual spatial interactions , 1994, Vision Research.

[17]  J. B. Levitt,et al.  Receptive fields and functional architecture of macaque V2. , 1994, Journal of neurophysiology.

[18]  Jochen Braun,et al.  Blindsight in normal observers , 1995, Nature.

[19]  C. Koch,et al.  Are we aware of neural activity in primary visual cortex? , 1995, Nature.

[20]  D. W. Heeley,et al.  Mechanisms Specialized for the Perception of Image Geometry , 1996, Vision Research.

[21]  H. Wilson,et al.  Fourier and Non-Fourier Pattern Discrimination Compared , 1996, Vision Research.

[22]  P. Cavanagh,et al.  Attentional resolution and the locus of visual awareness , 1996, Nature.

[23]  M. Morgan,et al.  Blindsight in normal subjects? , 1997, Nature.

[24]  R. Watt,et al.  The computation of orientation statistics from visual texture , 1997, Vision Research.

[25]  H. Wilson,et al.  Lateral interactions in peripherally viewed texture arrays. , 1997, Journal of the Optical Society of America. A, Optics, image science, and vision.

[26]  A B Watson,et al.  Psychophysica: Mathematica notebooks for psychophysical experiments (cinematica--psychometrica--quest). , 1997, Spatial vision.

[27]  M. Morgan,et al.  How the human visual system encodes the orientation of a texture, and why it makes mistakes , 1997, Current Biology.

[28]  M. Morgan,et al.  Visual Search for a Tilted Target: Tests of Spatial Uncertainty Models , 1998, The Quarterly journal of experimental psychology. A, Human experimental psychology.

[29]  S. Dakin.  Orientation variance as a quantifier of structure in texture. , 1999, Spatial vision.

[30]  D. Sagi,et al.  Mechanisms for spatial integration in visual detection: a model based on lateral interactions. , 1999, Spatial vision.

[31]  D. Sagi,et al.  Contrast integration across space , 1999, Vision Research.

[32]  A. Watson,et al.  Transducer model produces facilitation from opposite-sign flanks , 1999, Vision Research.

[33]  David C Burr,et al.  Feature-based integration of orientation signals in visual search , 2000, Vision Research.

[34]  M. Morgan,et al.  Facilitation from collinear flanks is cancelled by non-collinear flanks , 2000, Vision Research.

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

[36]  Preeti Verghese,et al.  The psychophysics of visual search , 2000, Vision Research.

[37]  J A Solomon,et al.  Odd-men-out are poorly localized in brief exposures. , 2001, Journal of vision.