Visual crowding

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Crowding makes a target that is easily recognizable in isolation, unrecognizable in clutter. When looking directly at the ‘+’ the letter ‘N’ presented in the right is more easily recognized than the N in the clutter ‘KND’

Visual crowding is the inability to view a target stimulus distinctly when presented in a clutter. Crowding impairs the ability to discriminate object features and contours among flankers, which in turn impairs people's ability to respond appropriately to the target stimulus.[1]

An operational definition of crowding explains what crowding is and how it is different from similar effects such as masking, lateral interaction and surround suppression; effects that make the target more challenging to see as well. There are different criteria that are used to differentiate crowding from these other effects. Firstly, crowding makes it difficult to identify an object but not detecting it among the clutter.[2][3][4] Crowded objects are collectively perceived to have high contrast, but they remain indistinct. The eccentricity of the target and the distance between the target and flankers influence crowding. As the distance between the target and the flankers' increases at a given eccentricity the ability to detect the target also improves as the eccentricity of a target is increased the more it pops out from the flankers and the more easily it is identified.[5]

Crowding is anisotropic, which means it has different values when measured in different directions. Radially positioned flankers make it harder to identify the target than tangentially positioned ones.[6] Crowding is stronger in the upper field of the four quadrants than the lower ones.[7] A recent study tells us that crowding is intense where the distractor and the target are in the same visual field than when they are in separate visual fields despite equal retinal distance.[8] Crowding is also asymmetrical meaning that a single flanker at an eccentric locus higher than the target makes it harder to identify the target than the single flanker at an eccentric locus closer to the fovea.[5] Crowding is not just a spatial phenomenon it happens over time as well, when a target is moving it is found to be more crowded when the flankers are leading than when they follow the target.[9]

Information that survives crowding[edit]

There is much information that gets through to peoples conscious even under the circumstances of crowding these include the appearance of a feature, people can easily perceive the appearance of a feature but cannot identify or discriminate the changes in this feature.[2][3][4][10] Secondly, After effects from adaptation survive crowding, adapting to a target in a crowded stimulus can help people form an orientation[8] and track the motion of the target.[11][12] Next is combined orientation, even though people are not able to tell the individual orientation of a target stimulus in a crowded setting, they can reliably report an average combined orientation of the stimulus, which means that the orientation signals from the target stimulus are combined than lost.[13]

Some target identity information survives crowding, people can identify more correct targets from a crowded setting when they are asked to report information on both the target and the flanker. Sometimes certain information such as the target information is lost, but the people are able to make better "target “ responses in this condition. Some information on the target is preserved, but most of the times the location information is lost.[14][15][16]

Reduction[edit]

Crowding is broken when the target and stimulus are different than when they are similar. The difference of target group from the flanker group of stimulus in shape, size,[17][18] orientation,[3][19][20] polarity,[21][17] spatial frequency,[22] depth,[17] color,[17][13][23] motion and order,[24] breaks crowding.  Crowding happens among faces(holistic crowding) having an inverted face flanker when searching for an upright face breaks crowding. Which makes upright faces more effective flankers.[25][26] Providing cue about the target location tends to reduce crowding.[27][15][28][29] Crowding is broken when the flankers are collectively masked, but this happens only when the flankers are masked with noise or using metacontrast masks but not with substitution masks.[30] When people are adapted to look for a target stimulus in a certain spatial position, it renders the flankers perceptually invisible (adaptation induced blindness), thus releasing the effect of crowding.[31]

Mechanism[edit]

Neurophysiological studies have not made much progress in narrowing down the locus of the brain at which crowding occurs. Previous researches have demonstrated that crowding is “dichoptical” meaning that the target is perceived by one eye and the distractor by the other.[32][33] Which should mean that the effect of crowding occurs in the cortex. Different researchers have claimed different sites to be the processing center for crowding e.g. (V1,[34] V2, V3,[35][36] V4[8][37][38] some researchers claim crowding happens at a later stage of visual processing[11][26]). So, the locus of the brain at which crowding occurs is still not clearly defined.

Models[edit]

From the many models that try and explain the process of crowding, there is still a lack of an actual model that helps predict the entirety of how crowding works. All models have three major division that remains as its essence: masking, pooling and substitution. The pooling can be of the low-level features or the pooling of attention. One of the model that nicely predicts is the model by Wilkinson where he boils down the process of crowding to the interaction between complex cells and simple cells, where the simple cells suppress weak complex cell responses and the complex cells respond actively resulted from spatial pooling and then they suppress simple cell activity in their receptive cell area[41].

Another model that best predicts crowding process proposes a quantitative model for a spatial integration of orientation signals, As per the principles of population coding, this model satisfactorily predicts properties like critical spacing, compulsory averaging and the inner and outer asymmetry.[18]

Levels[edit]

Different studies implicitly assume that crowding is a unitary effect due to a single stage of processing.[39][40] The other notion states that crowding happens independently at several stages of visual processing. This notion supports the view that crowding is influenced by the similarity and configuration of flankers and the target. By this notion, the effect is selectively observed between whole objects,[25][26] object parts,[41] and features.[39] This view is also consistent with Bouma's law. This view has gained much support. Crowding in a natural setting may also occur in layers depending on the location, content and attention dependence.

Bouma’s Law[edit]

Herman Bouma, a Dutch vision researcher and gerontologist stated, “For complete visual isolation of a letter presented at an eccentricity of φ deg, … no other letters should be present within (roughly) 0.5 φ distance."[5] At a later stage, he reduced the proportionality constant from 0.5 to 0.4.[19] This gave rise to the notion of “critical spacing” which is proportional to the eccentricity. Critical spacing is the sufficient distance needed for the identification of an object among its flankers in the retinotopically organized cortex. Bouma explains how the effect of crowding is dependent on the eccentricity of a subject and the distance between the flankers and the object. Many studies support the claim that critical space needed for crowding depends on the eccentricity of the subject.[2][3][4][42] The proportionality constant named b, after Bouma, is dependent on how similar the flankers are to the target, the number of possible targets, and the arbitrary threshold criterion.[40] The value of Boumas proportionality constant ‘b’ is different among studies, but most of the times it is reported to be ≈0.4 - 0.5. This rule is sometimes raised to the status of a 'law' but this remains controversial.

References[edit]

  1. ^ Whitney D, Levi DM (April 2011). "Visual crowding: a fundamental limit on conscious perception and object recognition". Trends in Cognitive Sciences. 15 (4): 160–8. doi:10.1016/j.tics.2011.02.005. PMC 3070834. PMID 21420894.
  2. ^ a b c Levi DM, Hariharan S, Klein SA (2002). "Suppressive and facilitatory spatial interactions in peripheral vision: peripheral crowding is neither size invariant nor simple contrast masking". Journal of Vision. 2 (2): 167–77. doi:10.1167/2.2.3. PMID 12678590.
  3. ^ a b c d Levi DM, Hariharan S, Klein SA (May 2002). "Suppressive and facilitatory spatial interactions in amblyopic vision". Vision Research. 42 (11): 1379–94. doi:10.1016/S0042-6989(02)00061-5. PMID 12044744.
  4. ^ a b c Pelli DG, Palomares M, Majaj NJ (December 2004). "Crowding is unlike ordinary masking: distinguishing feature integration from detection". Journal of Vision. 4 (12): 1136–69. doi:10.1167/4.12.12. PMID 15669917.
  5. ^ a b c Bouma H (April 1970). "Interaction effects in parafoveal letter recognition". Nature. 226 (5241): 177–8. Bibcode:1970Natur.226..177B. doi:10.1038/226177a0. PMID 5437004. S2CID 29459715.
  6. ^ Toet A, Levi DM (July 1992). "The two-dimensional shape of spatial interaction zones in the parafovea". Vision Research. 32 (7): 1349–57. doi:10.1016/0042-6989(92)90227-A. PMID 1455707. S2CID 8123408.
  7. ^ He S, Cavanagh P, Intriligator J (September 1996). "Attentional resolution and the locus of visual awareness". Nature. 383 (6598): 334–7. Bibcode:1996Natur.383..334H. doi:10.1038/383334a0. PMID 8848045. S2CID 4354509.
  8. ^ a b Liu T, Jiang Y, Sun X, He S (January 2009). "Reduction of the crowding effect in spatially adjacent but cortically remote visual stimuli". Current Biology. 19 (2): 127–32. doi:10.1016/j.cub.2008.11.065. PMC 3175242. PMID 19135367.
  9. ^ Bex PJ, Dakin SC, Simmers AJ (December 2003). "The shape and size of crowding for moving targets". Vision Research. 43 (27): 2895–904. doi:10.1016/S0042-6989(03)00460-7. PMID 14568377.
  10. ^ Levi DM, Carney T (December 2009). "Crowding in peripheral vision: why bigger is better". Current Biology. 19 (23): 1988–93. doi:10.1016/j.cub.2009.09.056. PMC 3045113. PMID 19853450.
  11. ^ a b Aghdaee SM (2005). "Adaptation to spiral motion in crowding condition". Perception. 34 (2): 155–62. doi:10.1068/p5298. PMID 15832566. S2CID 25291055.
  12. ^ Whitney D (May 2005). "Motion distorts perceived position without awareness of motion". Current Biology. 15 (9): R324-6. doi:10.1016/j.cub.2005.04.043. PMC 3890254. PMID 15886084.
  13. ^ a b Gheri C, Morgan MJ, Solomon JA (2007). "The relationship between search efficiency and crowding". Perception. 36 (12): 1779–87. doi:10.1068/p5595. PMC 2590853. PMID 18283928.
  14. ^ Popple AV, Levi DM (April 2005). "The perception of spatial order at a glance". Vision Research. 45 (9): 1085–90. doi:10.1016/j.visres.2004.11.008. PMID 15707915.
  15. ^ a b Strasburger H (December 2005). "Unfocused spatial attention underlies the crowding effect in indirect form vision". Journal of Vision. 5 (11): 1024–37. doi:10.1167/5.11.8. PMID 16441200.
  16. ^ Huckauf A, Knops A, Nuerk HC, Willmes K (November 2008). "Semantic processing of crowded stimuli?". Psychological Research. 72 (6): 648–56. doi:10.1007/s00426-008-0171-5. PMID 18841386. S2CID 10760582.
  17. ^ a b c d Kooi FL, Toet A, Tripathy SP, Levi DM (1994). "The effect of similarity and duration on spatial interaction in peripheral vision". Spatial Vision. 8 (2): 255–79. doi:10.1163/156856894X00350. PMID 7993878.
  18. ^ a b van den Berg R, Roerdink JB, Cornelissen FW (January 2010). "A neurophysiologically plausible population code model for feature integration explains visual crowding". PLOS Computational Biology. 6 (1): e1000646. Bibcode:2010PLSCB...6E0646V. doi:10.1371/journal.pcbi.1000646. PMC 2799670. PMID 20098499.
  19. ^ a b Andriessen JJ, Bouma H (January 1976). "Eccentric vision: adverse interactions between line segments". Vision Research. 16 (1): 71–8. doi:10.1016/0042-6989(76)90078-X. PMID 1258390. S2CID 23025320.
  20. ^ Danilova MV, Bondarko VM (November 2007). "Foveal contour interactions and crowding effects at the resolution limit of the visual system". Journal of Vision. 7 (2): 25.1–18. doi:10.1167/7.2.25. PMC 2652120. PMID 18217840.
  21. ^ Chakravarthi R, Cavanagh P (March 2007). "Temporal properties of the polarity advantage effect in crowding". Journal of Vision. 7 (2): 11.1–13. doi:10.1167/7.2.11. PMID 18217826.
  22. ^ Chung ST, Levi DM, Legge GE (June 2001). "Spatial-frequency and contrast properties of crowding". Vision Research. 41 (14): 1833–50. doi:10.1016/S0042-6989(01)00071-2. PMID 11369047.
  23. ^ Põder E, Wagemans J (November 2007). "Crowding with conjunctions of simple features". Journal of Vision. 7 (2): 23.1–12. doi:10.1167/7.2.23. PMID 18217838.
  24. ^ Chung ST, Li RW, Levi DM (March 2007). "Crowding between first- and second-order letter stimuli in normal foveal and peripheral vision". Journal of Vision. 7 (2): 10.1–13. doi:10.1167/7.2.10. PMC 2747649. PMID 18217825.
  25. ^ a b Farzin F, Rivera SM, Whitney D (June 2009). "Holistic crowding of Mooney faces". Journal of Vision. 9 (6): 18.1–15. doi:10.1167/9.6.18. PMC 2857385. PMID 19761309.
  26. ^ a b c Louie EG, Bressler DW, Whitney D (November 2007). "Holistic crowding: selective interference between configural representations of faces in crowded scenes". Journal of Vision. 7 (2): 24.1–11. doi:10.1167/7.2.24. PMC 3849395. PMID 18217839.
  27. ^ Yeshurun Y, Rashal E (August 2010). "Precueing attention to the target location diminishes crowding and reduces the critical distance". Journal of Vision. 10 (10): 16. doi:10.1167/10.10.16. PMID 20884481.
  28. ^ Chakravarthi R, Cavanagh P (June 2009). "Bilateral field advantage in visual crowding". Vision Research. 49 (13): 1638–46. doi:10.1016/j.visres.2009.03.026. PMC 2760476. PMID 19362572.
  29. ^ Freeman J, Pelli DG (October 2007). "An escape from crowding". Journal of Vision. 7 (2): 22.1–14. doi:10.1167/7.2.22. PMID 18217837.
  30. ^ Chakravarthi R, Cavanagh P (September 2009). "Recovery of a crowded object by masking the flankers: determining the locus of feature integration". Journal of Vision. 9 (10): 4.1–9. doi:10.1167/9.10.4. PMC 2766569. PMID 19810785.
  31. ^ Wallis TS, Bex PJ (February 2011). "Visual crowding is correlated with awareness". Current Biology. 21 (3): 254–8. doi:10.1016/j.cub.2011.01.011. PMC 3051843. PMID 21277208.
  32. ^ Flom MC, Heath GG, Takahashi E (November 1963). "Contour Interaction and Visual Resolution: Contralateral Effects". Science. 142 (3594): 979–80. Bibcode:1963Sci...142..979F. doi:10.1126/science.142.3594.979. PMID 14069233. S2CID 33685647.
  33. ^ Tripathy SP, Levi DM (May 1994). "Long-range dichoptic interactions in the human visual cortex in the region corresponding to the blind spot". Vision Research. 34 (9): 1127–38. doi:10.1016/0042-6989(94)90295-X. PMID 8184557. S2CID 15338292.
  34. ^ Pelli DG (August 2008). "Crowding: a cortical constraint on object recognition". Current Opinion in Neurobiology. 18 (4): 445–51. doi:10.1016/j.conb.2008.09.008. PMC 3624758. PMID 18835355.
  35. ^ Tyler CW, Likova LT (July 2007). "Crowding: a neuroanalytic approach". Journal of Vision. 7 (2): 16.1–9. doi:10.1167/7.2.16. PMID 18217831.
  36. ^ Bi T, Cai P, Zhou T, Fang F (October 2009). "The effect of crowding on orientation-selective adaptation in human early visual cortex". Journal of Vision. 9 (11): 13.1–10. doi:10.1167/9.11.13. PMID 20053076.
  37. ^ Motter BC (September 2006). "Modulation of transient and sustained response components of V4 neurons by temporal crowding in flashed stimulus sequences". The Journal of Neuroscience. 26 (38): 9683–94. doi:10.1523/JNEUROSCI.5495-05.2006. PMC 6674438. PMID 16988039.
  38. ^ Merigan WH (November 2000). "Cortical area V4 is critical for certain texture discriminations, but this effect is not dependent on attention". Visual Neuroscience. 17 (6): 949–58. doi:10.1017/S095252380017614X. PMID 11193111. S2CID 13095796.
  39. ^ a b Levi DM (February 2008). "Crowding--an essential bottleneck for object recognition: a mini-review". Vision Research. 48 (5): 635–54. doi:10.1016/j.visres.2007.12.009. PMC 2268888. PMID 18226828.
  40. ^ a b Pelli DG, Tillman KA (October 2008). "The uncrowded window of object recognition". Nature Neuroscience. 11 (10): 1129–35. doi:10.1038/nn.2187. PMC 2772078. PMID 18828191.
  41. ^ Martelli M, Majaj NJ, Pelli DG (February 2005). "Are faces processed like words? A diagnostic test for recognition by parts". Journal of Vision. 5 (1): 58–70. doi:10.1167/5.1.6. PMID 15831067.
  42. ^ Tripathy SP, Cavanagh P (September 2002). "The extent of crowding in peripheral vision does not scale with target size". Vision Research. 42 (20): 2357–69. doi:10.1016/S0042-6989(02)00197-9. PMID 12350424.
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